Question

我试图在一段时间后将4张图像设置为不可见和可见，如蓝色图像显示，蓝色图像隐藏，黄色图像显示，黄色图像隐藏。我想这样做没有事件，只有for循环。我正在尝试以下但它不起作用。我是android和图形的新手。请帮帮我

public class GameActivity extends Activity {    
/** Called when the activity is first created. */
private Handler mHandler = new Handler();
ImageView[] imViews = new ImageView[4];
ImageView imageView1;
ImageView imageView2;
ImageView imageView3;
ImageView imageView4;

@Override  
public void onCreate(Bundle savedInstanceState) {  
    super.onCreate(savedInstanceState);

    setContentView(R.layout.myviewlay);
    imageView1= (ImageView)findViewById(R.id.ImageView01);
    imageView2= (ImageView)findViewById(R.id.ImageView02);
    imageView3= (ImageView)findViewById(R.id.ImageView03);
    imageView4= (ImageView)findViewById(R.id.ImageView04);


    final ImageView[] imViews = new ImageView[4];
    imViews[0] = imageView1;
    imViews[1] = imageView2;
    imViews[2] = imageView3;
    imViews[3] = imageView4;

    mHandler.removeCallbacks(mUpdateTimeTask);                         
    mHandler.postDelayed(mUpdateTimeTask, 100); 

}

private Runnable mUpdateTimeTask = new Runnable() {  
     public void run() {   

         for(int i=0; i < 5; i++)
         {
              imViews[i].setVisibility(View.INVISIBLE);
              mHandler.postDelayed(this, 1000); 
              imViews[i].setVisibility(View.INVISIBLE);
              mHandler.postDelayed(this, 1000); 
         }

         }};   
}

我的错误日志：

04-23 05:25:16.383: ERROR/AndroidRuntime(506): java.lang.NullPointerException
04-23 05:25:16.383: ERROR/AndroidRuntime(506):     at com.games.game.GameActivity$1.run(GameActivity.java:60)
04-23 05:25:16.383: ERROR/AndroidRuntime(506):     at android.os.Handler.handleCallback(Handler.java:587)
04-23 05:25:16.383: ERROR/AndroidRuntime(506):     at android.os.Handler.dispatchMessage(Handler.java:92)
04-23 05:25:16.383: ERROR/AndroidRuntime(506):     at android.os.Looper.loop(Looper.java:123)
04-23 05:25:16.383: ERROR/AndroidRuntime(506):     at android.app.ActivityThread.main(ActivityThread.java:3647)
04-23 05:25:16.383: ERROR/AndroidRuntime(506):     at java.lang.reflect.Method.invokeNative(Native Method)
04-23 05:25:16.383: ERROR/AndroidRuntime(506):     at java.lang.reflect.Method.invoke(Method.java:507)
04-23 05:25:16.383: ERROR/AndroidRuntime(506):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
04-23 05:25:16.383: ERROR/AndroidRuntime(506):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
04-23 05:25:16.383: ERROR/AndroidRuntime(506):     at dalvik.system.NativeStart.main(Native Method)

Answer 1

尝试使用：

imViews[i].setVisibility(View.GONE);

同样如@MByD所说，通过只调用一次来改进你的代码。

Answer 2

你无法通过使用postDelayed（）来实现这一点。该方法不会在循环中暂停您的方法。使用Thread.sleep（）可以实现。但是，在UI线程上执行此操作最终会导致强制关闭，因为您将阻止UI线程太长时间。

基本上你需要某种后台线程，等待你，然后将一个runnable发布到显示/隐藏视图的UI线程。

private Runnable mUpdateTimeTask = new Runnable() {  
 public void run() {   

     for(int i=0; i < 5; i++)
     {
          final ImageView view = imViews[i];
          mHandler.post(new Runnable() {
              public void run() {
                  view.setVisibility(View.INVISIBLE);
              }
          });
          try {
              Thread.sleep(1000);
          } catch (Exception e) {} 
          mHandler.post(new Runnable() {
              public void run() {
                  view.setVisibility(View.VISIBLE);
              }
          });              
          try {
              Thread.sleep(1000);
          } catch (Exception e) {}         
     }

     }};   
}

在onCreate（）方法中，用：

启动它

new Thread(mUpdateTimeTask).start();

您可能还想查看TimerTask课程，该课程可以帮助您定期运行内容。有几种方法可以做这些事情。

UI线程的Android帮助新手

2 个答案: