Android 7.1.1後退按鈕方法不被稱爲

Question

我正在開發運行Android 7.1.1的Google Pixel。

以下是2項活動，PlayActivity和ScoreScreenActivity。流程看起來應該像Main> Play> Game> Score> [back button]> Play> [back button]> Main。

在ScoreScreenActivity中按下後退按鈕時，會調用onKeyPressed（）方法。我們被重定向到PlayActivity。到現在爲止還挺好。現在我們處於PlayActivity中，當再次按下後退按鈕時，我們將不正確地從名爲ScoreScreenActivity的Activity重定向回GameActivity。我們應該將其發送給MainActivity。

另外，我在GameActivity的startActivity（）和ScoreScreenActivity中完成了（）。

W/ViewRootImpl[ScoreScreenActivity]: Cancelling event due to no window focus: KeyEvent 

這裏有活動代碼： 不是功能代碼：

public class PlayActivity extends AppCompatActivity { 

@Override 
protected void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.activity_play); 

    Button mOneMinute = (Button) findViewById(R.id.play_one_minute); 
    if (mOneMinute!=null){ 
     mOneMinute.setOnClickListener(new View.OnClickListener() { 
      @Override 
      public void onClick(View view) { 
       Intent intent = new Intent(PlayActivity.this, GameActivity.class); 
       startActivity(intent); 
       finish(); 
      } 
     }); 

    } 
} 
@Override 
public void onBackPressed(){ 
    System.out.println("this isn't printed either"); 
    // AlertDialog happens here 
} 
// Copy & Pasted from another StackOverFlow (http://stackoverflow.com/questions/16646301/onbackpressed-is-not-being-called) 
@Override 
public boolean onKeyDown(int keyCode, KeyEvent event) { 
    System.out.println("never gets printed"); 
    if (keyCode == KeyEvent.KEYCODE_BACK) { 
     Log.d("back", "should go back to MainActivity"); 
     Intent i=new Intent(PlayActivity.this, MainActivity.class); 
     startActivity(i); 
     finish(); 
    } 
    return true; 
} 

功能碼：

public class ScoreScreenActivity extends AppCompatActivity { 

    @Override 
    protected void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.activity_score_screen); 
     int score = 0; 
     Intent intent = getIntent(); 
     score = intent.getIntExtra("mScore", score); 
     System.out.println(score); 

     TextView mTV = (TextView) findViewById(R.id.score_text); 
     if (mTV != null){ 
      mTV.setTextSize(20); 
      mTV.setTextAlignment(View.TEXT_ALIGNMENT_CENTER); 
      String str = "Well Done!\nYour Score: "+ score +"\nThere's no high score system for now,\n" + 
        "so remember this score\nif it's a new high score!"; 
      SpannableString ss = new SpannableString(str); 
      ss.setSpan(new RelativeSizeSpan(2), 0, 25, 0); 
      mTV.setText(ss); 
     } 
     Button mReturn = (Button) findViewById(R.id.score_return); 
     if (mReturn!= null){ 
      mReturn.setOnClickListener(new View.OnClickListener() { 
       @Override 
       public void onClick(View view) { 
        Intent returnIntent = new Intent(ScoreScreenActivity.this, MainActivity.class); 
        startActivity(returnIntent); 
       } 
      }); 
     } 

    } 

    @Override 
    public void onBackPressed(){ 
     System.out.println("this does not get printed"); 
     // AlertDialog happens here 
    } 

    // Copy & Pasted from another StackOverFlow (http://stackoverflow.com/questions/16646301/onbackpressed-is-not-being-called) 
    @Override 
    public boolean onKeyDown(int keyCode, KeyEvent event) { 
     System.out.println("this gets printed"); 
     if (keyCode == KeyEvent.KEYCODE_BACK) { 
      Log.e("back",""+1); 
      Intent i=new Intent(ScoreScreenActivity.this,PlayActivity.class); 
      startActivity(i); 
      finish(); 
     } 
     return true; 
    } 
} 

Answer 1

而且，當我們從ScoreScreenActivity去PlayActivity被顯示此錯誤你可以這樣處理：

的API 5級和更大的（新）

@Override 
public void onBackPressed() { 
    // your code. 
} 

比API年長5

@Override 
public boolean onKeyDown(int keyCode, KeyEvent event) { 
    if (keyCode == KeyEvent.KEYCODE_BACK) { 
     // your code 
     return true; 
    } 

    return super.onKeyDown(keyCode, event); // u are missing this 
}