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本文介紹了Android 操作欄選項卡和鍵盤焦點的處理方法，對大家解決問題具有一定的參考價值，需要的朋友們下面隨著小編來一起學習吧！

問題描述

我有一個包含兩個選項卡的非常簡單的活動，我正在嘗試在自定義視圖中處理鍵盤輸入.這很好用......直到我交換標簽.一旦我交換標簽，我就再也無法捕捉到這些事件了.然而，在另一個應(yīng)用程序中，打開一個對話框然后關(guān)閉它會允許我的關(guān)鍵事件通過.如果不這樣做，我將無法再次獲取我的關(guān)鍵事件.

I have a very simple activity with two tabs, and I'm trying to handle keyboard input in a custom view. This works great... until I swap tabs. Once I swap tabs, I can never get the events to capture again. In another application, opening a Dialog and then closing it, however, would allow my key events to go through. Without doing that I've found no way of getting my key events again.

這里有什么問題?一旦我交換標簽，我就找不到任何方法來獲取關(guān)鍵事件，并且很好奇是什么在吃它們.這個例子很簡短.

What's the issue here? I can't find any way to get key events once I swap tabs, and am curious what's eating them. This example is pretty short and to the point.

<?xml version="1.0" encoding="utf-8"?>
    <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
      android:orientation="vertical"
      android:layout_width="fill_parent"
      android:layout_height="fill_parent"
    >
    <FrameLayout
      android:id="@+id/actionbar_content" 
      android:layout_width="match_parent"
      android:layout_height="match_parent"
    />
</LinearLayout>

my_fragment.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
  xmlns:android="http://schemas.android.com/apk/res/android"
  android:orientation="vertical"
  android:layout_width="match_parent"
  android:layout_height="match_parent">
    <view 
      class="com.broken.keyboard.KeyboardTestActivity$MyView"
      android:background="#777777"
      android:focusable="true"
      android:focusableInTouchMode="true"
      android:layout_width="fill_parent"
      android:layout_height="fill_parent"
    >
        <requestFocus/>
    </view>
</LinearLayout>

KeyboardTestActivity.java

package com.broken.keyboard;

import android.app.ActionBar;
import android.app.Activity;
import android.app.Fragment;
import android.app.FragmentManager;
import android.os.Bundle;
import android.util.AttributeSet;
import android.util.Log;
import android.view.KeyEvent;
import android.view.LayoutInflater;
import android.view.MotionEvent;
import android.view.View;
import android.view.ViewGroup;
import android.view.inputmethod.InputMethodManager;

import android.app.FragmentTransaction;
import android.app.ActionBar.Tab;
import android.content.Context;

public class KeyboardTestActivity extends Activity {

    public static class MyView extends View {
        public void toggleKeyboard()
        { ((InputMethodManager)getContext().getSystemService(Context.INPUT_METHOD_SERVICE)).toggleSoftInput(0, 0); }

        public MyView(Context context)
        { super(context); }

        public MyView(Context context, AttributeSet attrs)
        { super(context, attrs); }

        public MyView(Context context, AttributeSet attrs, int defStyle)
        { super(context, attrs, defStyle); }


        // FIRST PLACE I TRY, WHERE I WANT TO GET THE PRESSES
        @Override
        public boolean onKeyDown(int keyCode, KeyEvent event) {
            Log.i("BDBG", "Key went down in view!");
            return super.onKeyDown(keyCode,event);
        }

        // Toggle keyboard on touch!
        @Override
        public boolean onTouchEvent(MotionEvent event)
        {
            if ((event.getAction() & MotionEvent.ACTION_MASK) == MotionEvent.ACTION_DOWN)
            {
                toggleKeyboard();
            }
            return super.onTouchEvent(event);
        }
    }

    // Extremely simple fragment
    public class MyFragment extends Fragment {        
        @Override
        public View onCreateView (LayoutInflater inflater, ViewGroup container,
                Bundle savedInstanceState) {
            View v = inflater.inflate(R.layout.my_fragment, container, false);
            return v;
        }
    }

    // Simple tab listener
    public static class MyTabListener implements ActionBar.TabListener
    {
        private FragmentManager mFragmentManager=null;
        private Fragment mFragment=null;
        private String mTag=null;
        public MyTabListener(FragmentManager fragmentManager, Fragment fragment,String tag)
        {
            mFragmentManager=fragmentManager;
            mFragment=fragment;
            mTag=tag;
        }
        @Override
        public void onTabReselected(Tab tab, FragmentTransaction ft) {
            // do nothing
        }

        @Override
        public void onTabSelected(Tab tab, FragmentTransaction ft) {
            mFragmentManager.beginTransaction()
                .replace(R.id.actionbar_content, mFragment, mTag)
                .commit();
        }

        @Override
        public void onTabUnselected(Tab tab, FragmentTransaction ft) {
            mFragmentManager.beginTransaction()
                .remove(mFragment)
                .commit();
        }

    }

    FragmentManager mFragmentManager;
    ActionBar mActionBar;

    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        // Retrieve the fragment manager
        mFragmentManager=getFragmentManager();
        mActionBar=getActionBar();

        // remove the activity title to make space for tabs
        mActionBar.setDisplayShowTitleEnabled(false);

        mActionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);

        // Add the tabs
        mActionBar.addTab(mActionBar.newTab()
                .setText("Tab 1")
                .setTabListener(new MyTabListener(getFragmentManager(), new MyFragment(),"Frag1")));

        mActionBar.addTab(mActionBar.newTab()
                .setText("Tab 2")
                .setTabListener(new MyTabListener(getFragmentManager(), new MyFragment(),"Frag2")));


    }

    // OTHER PLACE I TRY, DOESN'T WORK BETTER THAN IN THE VIEW
    @Override
    public boolean onKeyDown(int keyCode, KeyEvent event) {
        Log.i("BDBG", "Key went down in activity!");
        return super.onKeyDown(keyCode,event);
    }
}

推薦答案

我已經(jīng)解決了自己的問題，所以我想我會分享解決方案.如果有一些措辭問題，請在評論中糾正我；我盡量做到準確，但我并不完全是安卓專家.這個答案也應(yīng)該作為一個很好的例子來說明如何處理一般的換出 ActionBar 選項卡.不管你是否喜歡解決方案代碼的設(shè)計，它應(yīng)該是有用的.

I've solved my own problem, so I thought I'd share the solution. If there's some wording issue, please correct me in a comment; I'm trying to be as accurate as I can but I'm not entirely an android expert. This answer should also serve as an excellent example of how to handle swapping out ActionBar tabs in general. Whether or not one likes the design of the solution code, it should be useful.

以下鏈接幫助我找出了我的問題:http://code.google.com/p/android/issues/detail?id=2705

The following link helped me figure out my issue: http://code.google.com/p/android/issues/detail?id=2705

事實證明，手頭有兩個重要問題.首先，如果一個 View 既是 android:focusable 又是 android:focusableInTouchMode，那么在蜂窩平板電腦上，人們可能會期望點擊它和類似的東西會聚焦它.然而，這不一定是真的.如果該視圖恰好也是 android:clickable，那么確實點擊會聚焦該視圖.如果它不可點擊，它不會被觸摸聚焦.

It turns out, there are two important issues at hand. Firstly, if a View is both android:focusable and android:focusableInTouchMode, then on a honeycomb tablet one might expect that tapping it and similar would focus it. This, however, is not necessarily true. If that View happens to also be android:clickable, then indeed tapping will focus the view. If it is not clickable, it will not be focused by touch.

此外，當換出片段時，會出現(xiàn)與第一次為活動實例化視圖時非常相似的問題.只有在完全準備好視圖層次結(jié)構(gòu)后，才需要進行某些更改.

Furthermore, when swapping out a fragment there's an issue very similar to when first instantiating the view for an activity. Certain changes need to be made only after the View hierarchy is completely prepared.

如果在視圖層次結(jié)構(gòu)完全準備好之前對片段內(nèi)的視圖調(diào)用requestFocus()"，則視圖確實會認為它已聚焦；但是，如果軟鍵盤啟動，它實際上不會向該視圖發(fā)送任何事件！更糟糕的是，如果那個 View 是可點擊的，此時點擊它并不能解決這個鍵盤焦點問題，因為 View 認為它確實是焦點，沒有什么可做的.但是，如果要聚焦某個其他視圖，然后再點擊該視圖，因為它既可點擊又可聚焦，它確實會聚焦并將鍵盤輸入定向到該視圖.

If you call "requestFocus()" on a view within a fragment before the View hierarchy is completely prepared, the View will indeed think that it is focused; however, if the soft keyboard is up, it will not actually send any events to that view! Even worse, if that View is clickable, tapping it at this point will not fix this keyboard focus issue, as the View thinks that it is indeed focused and there is nothing to do. If one was to focus some other view, and then tap back onto this one, however, as it is both clickable and focusable it would indeed focus and also direct keyboard input to this view.

鑒于該信息，在切換到選項卡時設(shè)置焦點的正確方法是在切換到片段后將可運行對象發(fā)布到片段的視圖層次結(jié)構(gòu)，然后才調(diào)用 requestFocus().在視圖層次結(jié)構(gòu)完全準備好之后調(diào)用 requestFocus() 將聚焦視圖以及直接鍵盤輸入到它，如我們所愿.它不會進入那種奇怪的焦點狀態(tài)，即視圖聚焦但鍵盤輸入不知何故沒有指向它，如果在視圖層次結(jié)構(gòu)完全準備好之前調(diào)用 requestFocus() 就會發(fā)生這種情況.

Given that information, the correct approach to setting the focus upon swapping to a tab is to post a runnable to the View hierarchy for the fragment after it is swapped in, and only then call requestFocus(). Calling requestFocus() after the View hierarchy is fully prepared will both focus the View as well as direct keyboard input to it, as we want. It will not get into that strange focused state where the view is focused but the keyboard input is somehow not directed to it, as will happen if calling requestFocus() prior to the View hierarchy being fully prepared.

同樣重要的是，在片段布局的 XML 中使用requestFocus"標簽會過早調(diào)用 requestFocus().沒有理由在片段的布局中使用該標簽.在片段之外，也許.. 但不在片段之內(nèi).

Also important, using the "requestFocus" tag within the XML of a fragment's layout will most call requestFocus() too early. There is no reason to ever use that tag in a fragment's layout. Outside of a fragment, maybe.. but not within.

在代碼中，我在片段頂部添加了一個 EditText，僅用于測試點擊焦點更改行為，點擊自定義視圖也會切換軟鍵盤.交換選項卡時，焦點也應(yīng)默認為自定義視圖.我試圖有效地注釋代碼.

In the code, I've added an EditText to the top of the fragment just for testing tap focus change behaviors, and tapping the custom View will also toggle the soft keyboard. When swapping tabs, the focus should also default to the custom view. I tried to comment the code effectively.

package com.broken.keyboard;

import android.app.ActionBar;
import android.app.Activity;
import android.app.Fragment;
import android.app.FragmentManager;
import android.os.Bundle;
import android.util.AttributeSet;
import android.util.Log;
import android.view.KeyEvent;
import android.view.LayoutInflater;
import android.view.MotionEvent;
import android.view.View;
import android.view.ViewGroup;
import android.view.inputmethod.InputMethodManager;

import android.app.FragmentTransaction;
import android.app.ActionBar.Tab;
import android.content.Context;

public class KeyboardTestActivity extends Activity {

    /**
     * This class wraps the addition of tabs to the ActionBar,
     * while properly swapping between them.  Furthermore, it
     * also provides a listener interface by which you can
     * react additionally to the tab changes.  Lastly, it also
     * provides a callback for after a tab has been changed and
     * a runnable has been post to the View hierarchy, ensuring
     * the fragment transactions have completed.  This allows
     * proper timing of a call to requestFocus(), and other
     * similar methods.
     * 
     * @author nacitar sevaht
     *
     */
    public static class ActionBarTabManager 
    {
        public static interface TabChangeListener
        {
            /**
             * Invoked when a new tab is selected.
             * 
             * @param tag The tag of this tab's fragment.
             */
            public abstract void onTabSelected(String tag);

            /**
             * Invoked when a new tab is selected, but after
             * a Runnable has been executed after being post
             * to the view hierarchy, ensuring the fragment
             * transaction is complete.
             * 
             * @param tag The tag of this tab's fragment.
             */
            public abstract void onTabSelectedPost(String tag);

            /**
             * Invoked when the currently selected tab is reselected.
             * 
             * @param tag The tag of this tab's fragment.
             */
            public abstract void onTabReselected(String tag);

            /**
             * Invoked when a new tab is selected, prior to {@link onTabSelected}
             * notifying that the previously selected tab (if any) that it is no
             * longer selected.
             * 
             * @param tag The tag of this tab's fragment.
             */
            public abstract void onTabUnselected(String tag);


        }

        // Variables
        Activity mActivity = null;
        ActionBar mActionBar = null;
        FragmentManager mFragmentManager = null;
        TabChangeListener mListener=null;
        View mContainer = null;
        Runnable mTabSelectedPostRunnable = null;

        /**
         * The constructor of this class.
         * 
         * @param activity The activity on which we will be placing the actionbar tabs.
         * @param containerId The layout id of the container, preferable a  {@link FrameLayout}
         *        that will contain the fragments.
         * @param listener A listener with which one can react to tab change events.
         */
        public ActionBarTabManager(Activity activity, int containerId, TabChangeListener listener)
        {
            mActivity = activity;
            if (mActivity == null)
                throw new RuntimeException("ActionBarTabManager requires a valid activity!");

            mActionBar = mActivity.getActionBar();
            if (mActionBar == null)
                throw new RuntimeException("ActionBarTabManager requires an activity with an ActionBar.");

            mContainer = activity.findViewById(containerId);

            if (mContainer == null)
                throw new RuntimeException("ActionBarTabManager requires a valid container (FrameLayout, preferably).");

            mListener = listener;
            mFragmentManager = mActivity.getFragmentManager();

            // Force tab navigation mode
            mActionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);
        }

        /**
         * Simple Runnable to invoke the {@link onTabSelectedPost} method of the listener.
         * 
         * @author nacitar sevaht
         *
         */
        private class TabSelectedPostRunnable implements Runnable
        {
            String mTag = null;
            public TabSelectedPostRunnable(String tag)
            {
                mTag=tag;
            }
            @Override
            public void run() {
                if (mListener != null) {
                    mListener.onTabSelectedPost(mTag);
                }
            }

        }

        /**
         * Internal TabListener.  This class serves as a good example
         * of how to properly handles swapping the tabs out.  It also
         * invokes the user's listener after swapping.
         * 
         * @author nacitar sevaht
         *
         */
        private class TabListener implements ActionBar.TabListener
        {
            private Fragment mFragment=null;
            private String mTag=null;
            public TabListener(Fragment fragment, String tag)
            {
                mFragment=fragment;
                mTag=tag;
            }
            private boolean post(Runnable runnable)
            {
                return mContainer.post(runnable);
            }
            @Override
            public void onTabReselected(Tab tab, FragmentTransaction ft) {
                // no fragment swapping logic necessary

                if (mListener != null) {
                    mListener.onTabReselected(mTag);
                }

            }
            @Override
            public void onTabSelected(Tab tab, FragmentTransaction ft) {
                mFragmentManager.beginTransaction()
                    .replace(mContainer.getId(), mFragment, mTag)
                    .commit();
                if (mListener != null) {
                    mListener.onTabSelected(mTag);
                }
                // Post a runnable for this tab
                post(new TabSelectedPostRunnable(mTag));
            }

            @Override
            public void onTabUnselected(Tab tab, FragmentTransaction ft) {
                mFragmentManager.beginTransaction()
                    .remove(mFragment)
                    .commit();
                if (mListener != null) {
                    mListener.onTabUnselected(mTag);
                }
            }

        }

        /**
         * Simple wrapper for adding a text-only tab.  More robust
         * approaches could be added.
         * 
         * @param title The text to display on the tab.
         * @param fragment The fragment to swap in when this tab is selected.
         * @param tag The unique tag for this tab.
         */
        public void addTab(String title, Fragment fragment, String tag)
        {
            // The tab listener is crucial here.
            mActionBar.addTab(mActionBar.newTab()
                    .setText(title)
                    .setTabListener(new TabListener(fragment, tag)));   
        }

    }
    /**
     * A simple custom view that toggles the on screen keyboard when touched,
     * and also prints a log message whenever a key event is received.
     * 
     * @author nacitar sevaht
     *
     */
    public static class MyView extends View {
        public void toggleKeyboard()
        { ((InputMethodManager)getContext().getSystemService(Context.INPUT_METHOD_SERVICE)).toggleSoftInput(0, 0); }

        public MyView(Context context)
        { super(context); }

        public MyView(Context context, AttributeSet attrs)
        { super(context, attrs); }

        public MyView(Context context, AttributeSet attrs, int defStyle)
        { super(context, attrs, defStyle); }


        @Override
        public boolean onKeyDown(int keyCode, KeyEvent event) {
            Log.i("BDBG", "Key (" + keyCode + ") went down in the custom view!");
            return true;
        }

        // Toggle keyboard on touch!
        @Override
        public boolean onTouchEvent(MotionEvent event)
        {
            if ((event.getAction() & MotionEvent.ACTION_MASK) == MotionEvent.ACTION_DOWN)
            {
                toggleKeyboard();
            }
            return super.onTouchEvent(event);
        }
    }

    // Extremely simple fragment
    public class MyFragment extends Fragment {
        @Override
        public View onCreateView (LayoutInflater inflater, ViewGroup container,
                Bundle savedInstanceState) {
            View v = inflater.inflate(R.layout.my_fragment, container, false);
            return v;
        }
    }

    public class MyTabChangeListener implements ActionBarTabManager.TabChangeListener
    {
        public void onTabReselected(String tag) { }
        public void onTabSelected(String tag) { }
        public void onTabSelectedPost(String tag)
        {
            // TODO: NOTE: typically, one would conditionally set the focus based upon the tag.
            //             but in our sample, both tabs have the same fragment layout.
            View view=findViewById(R.id.myview);
            if (view == null)
            {
                throw new RuntimeException("Tab with tag of (""+tag+"") should have the view we're looking for, but doesn't!");
            }
            view.requestFocus();
        }
        public void onTabUnselected(String tag) { }
    }

    // Our tab manager
    ActionBarTabManager mActionBarTabManager = null;

    // Our listener
    MyTabChangeListener mListener = new MyTabChangeListener();

    // Called when the activity is first created.
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        // instantiate our tab manager
        mActionBarTabManager = new ActionBarTabManager(this,R.id.actionbar_content,mListener);

        // remove the activity title to make space for tabs
        getActionBar().setDisplayShowTitleEnabled(false);

        // Add the tabs
        mActionBarTabManager.addTab("Tab 1", new MyFragment(), "Frag1");
        mActionBarTabManager.addTab("Tab 2", new MyFragment(), "Frag2");
    }
}

main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    >
    <FrameLayout
        android:id="@+id/actionbar_content" 
        android:layout_width="match_parent"
        android:layout_height="match_parent"
    />
</LinearLayout>

my_fragment.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
  xmlns:android="http://schemas.android.com/apk/res/android"
  android:orientation="vertical"
  android:layout_width="match_parent"
  android:layout_height="match_parent">
    <EditText
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        />

    <!-- note that view is in lower case here -->
    <view 
        class="com.broken.keyboard.KeyboardTestActivity$MyView"
        android:id="@+id/myview"
        android:background="#777777"
        android:clickable="true"
        android:focusable="true"
        android:focusableInTouchMode="true"
        android:layout_width="fill_parent"
        android:layout_height="match_parent"
    />
</LinearLayout>

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Android 操作欄選項卡和鍵盤焦點

問題描述

my_fragment.xml

KeyboardTestActivity.java

推薦答案

main.xml

my_fragment.xml

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