線程前的按鈕背景

Question

爲什麼在線程啓動之前按鈕的背景沒有改變？線程休眠結束後它會改變。我提到，如果沒有線程，背景會發生變化。

answer1Top.setBackgroundDrawable(correct); 
try { 
    Thread.sleep(2000); 
} catch (InterruptedException e) { 
    e.printStackTrace(); 
} 

//I want to stop this 
playerScTop--; 
playerScoreTop.setText(String.valueOf(playerScTop)); 

Answer 1

創建延伸AsyncTask一個新的類，它傳遞View其改變背景以及兩個後臺Drawable實例，則：

在 onPreExecute()（上UI線程運行）
• ，設置第一背景上繪製的視圖
• 在doInBackground()（運行在後臺線程），睡眠2秒
• 在onPostExecute()（運行Ò ñUI線程），設置其它可繪製你的看法

未經測試示例代碼：

public class BackgroundChangeTask extends AsyncTask<Void, Void, Void> { 

    private View view; 
    private Drawable background1; 
    private Drawable background2; 

    public BackgroundChangeTask(View view, Drawable background1, Drawable background2) { 
     this.view = view; 
     this.background1 = background1; 
     this.background2 = background2; 
    } 

    @Override 
    protected void onPreExecute() { 
     view.setBackgroundDrawable(background1); 
    } 

    @Override 
    protected Void doInBackground(Void... params) { 
     try { 
      Thread.sleep(2000); 
     } catch (InterruptedException e) { 
      // too bad 
     } 
     return null; 
    } 

    @Override 
    protected void onPostExecute(Void result) { 
     view.setBackgroundDrawable(background2); 

     // add anything else you want to run "after 2 seconds" here, e.g. 
     playerScTop--; 
     playerScoreTop.setText(String.valueOf(playerScTop)); 
    } 
} 

調用從活動/片段/等這樣的（無需保持創建的任務各地在現場）：

new BackgroundChangeTask(BackgroundChangeTask, correct, theOtherDrawable).execute(); 

Answer 2

answer1Top.setBackgroundDrawable(correct); 

new Handler().postDelayed(new Runnable() { 

    @Override 
    public void run() { 
      playerScTop--; 
      playerScoreTop.setText(String.valueOf(playerScTop)); 
    } 

}, 2000);