android - View.OnKeyListener 为我的 Activity 工作过一次，不再工作

Question

我有一个实现了 View.OnKeyListener 的 Activity，以便它可以在用户点击后退按钮时捕捉并弹出一个对话框。以前，它工作得很好。然而，最近它停止工作了，应用程序会假装没有 onKey 方法来捕获后退按钮。我似乎无法弄清楚为什么，因为自从我进行更改后我几乎没有触及 onKey 方法。我尝试只使用 OnBackPressed() 代替，但这并没有解决任何问题，而且实际上造成了奇怪且不可预测的行为。谁能帮我弄清楚为什么我的应用似乎让系统控制了后退按钮？

以下是我实现的重要部分:

import com.actionbarsherlock.app.ActionBar;
import com.actionbarsherlock.app.SherlockFragmentActivity;
import com.actionbarsherlock.view.Menu;
import com.actionbarsherlock.view.MenuItem;
import com.actionbarsherlock.view.MenuInflater;
import android.app.AlertDialog;
import android.content.DialogInterface;
import android.content.Intent;
import android.content.SharedPreferences;
import android.os.Bundle;
import android.preference.PreferenceManager;
import android.view.KeyEvent;
import android.view.View;

public class NagTasksAddTasksActivity extends SherlockFragmentActivity implements View.OnKeyListener {
    //various parameters
    public void onCreate(Bundle savedInstanceBundle)
    {
        super.onCreate(savedInstanceBundle);
        SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(getBaseContext());
        String setTheme = prefs.getString("themeselect", "Dark Overflow");
        if (setTheme.toLowerCase().contentEquals("dark overflow")){
            setTheme(R.style.Theme_Sherlock_ForceOverflow);
        } else if (setTheme.toLowerCase().contentEquals("light overflow")){
            setTheme(R.style.Theme_Sherlock_Light_ForceOverflow);
            isDarkThemeUsed = false;
        } else if (setTheme.toLowerCase().contentEquals("dark menu")){
            setTheme(R.style.Theme_Sherlock);
        } else if (setTheme.toLowerCase().contentEquals("light menu")){
            setTheme(R.style.Theme_Sherlock_Light);
            isDarkThemeUsed = false;
        }
        setContentView(R.layout.createtasklayout);
        ActionBar actionBar = getSupportActionBar();
        setTitle(R.string.newTask);

    }
    ...
    @Override
    public boolean onKey(View v, int keyCode, KeyEvent event) {
        if (keyCode == KeyEvent.KEYCODE_BACK)
        {
            AlertDialog.Builder builder = new AlertDialog.Builder(this);
            builder.setCancelable(true);
            builder.setTitle(R.string.wait);
            builder.setMessage(R.string.confirmbackkey);
            builder.setPositiveButton(R.string.save, new DialogInterface.OnClickListener() {

                @Override
                public void onClick(DialogInterface dialog, int which) {
                    //stuff
                    dialog.dismiss();
                }
            });
            builder.setNegativeButton(R.string.discard, new DialogInterface.OnClickListener() {

                @Override
                public void onClick(DialogInterface dialog, int which) {
                    AlertDialog.Builder subBuilder = new AlertDialog.Builder(getParent());
                    subBuilder.setCancelable(true);
                    subBuilder.setTitle(R.string.wait);
                    subBuilder.setMessage(R.string.confirmdiscard);
                    subBuilder.setPositiveButton(R.string.yes, new DialogInterface.OnClickListener() {

                        @Override
                        public void onClick(DialogInterface dialog, int which) {
                            //more stuff
                            dialog.dismiss();
                        }
                    });
                    subBuilder.setNegativeButton(R.string.no, new DialogInterface.OnClickListener() {

                        @Override
                        public void onClick(DialogInterface dialog, int which) {
                            dialog.cancel();
                        }
                    });
                    dialog.dismiss();
                    subBuilder.create().show();
                }
            });
            builder.setNeutralButton(R.string.cancel, new DialogInterface.OnClickListener() {

                @Override
                public void onClick(DialogInterface dialog, int which) {
                    dialog.cancel();
                }
            });
            builder.create().show();
            return true;
        }
        return false;
    }
}

Answer 1

捕获后退按钮的另一种方法是在 Activity 中使用 dispatchKeyEvent 方法(您不需要实现 View.OnKeyListener)。这似乎每次都对我有用。

public class HomeActivity extends Activity
{
...

    @Override
    public boolean dispatchKeyEvent(KeyEvent event) 
    {
        int action = event.getAction();
        int keyCode = event.getKeyCode();
        switch (keyCode) 
        {
            case KeyEvent.KEYCODE_BACK:
                if (action == KeyEvent.ACTION_DOWN)
                {
                    Log.v("myApp", "Back button pressed.");
                    return true;
                }
            default:
                return false;
        }
        return false;
    }
}