Android中的运行时错误

Question

public class MainActivity extends AppCompatActivity {
 ConstraintLayout cl;
int i;
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    cl=(ConstraintLayout)findViewById(R.id.cl);
    cl.setBackgroundResource(R.drawable.bb1);
    i=0;
 new Timer().scheduleAtFixedRate(new TimerTask() {
       @Override
        public void run() {
          cl.animate().alpha(0f).setDuration(1500);
            if(i==0)
              cl.setBackgroundResource(R.drawable.bb1);
            else if(i==1)
                cl.setBackgroundResource(R.drawable.bb2);
            else if(i==2)
                cl.setBackgroundResource(R.drawable.bb3);
            else if(i==3)
                cl.setBackgroundResource(R.drawable.bb4);
            else if(i==4)
                cl.setBackgroundResource(R.drawable.bb5);
            else if(i==5)
                cl.setBackgroundResource(R.drawable.bb6);
           i++;
           cl.animate().alpha(1f).setDuration(1500);
        }
    },0,3000);
}

}

错误 ：

E / AndroidRuntime：致命异常：Timer-0

                                                                        android.view.ViewRootImpl$CalledFromWrongThreadException: Only the original thread that created a view hierarchy can touch its views.
                                                                            at android.view.ViewRootImpl.checkThread(ViewRootImpl.java:6902)
                                                                            at android.view.ViewRootImpl.invalidateChildInParent(ViewRootImpl.java:1087)
                                                                            at android.view.ViewGroup.invalidateChild(ViewGroup.java:5246)
                                                                            at android.view.View.invalidateInternal(View.java:13573)
                                                                            at android.view.View.invalidate(View.java:13509)
                                                                            at android.view.View.invalidateDrawable(View.java:17693)
                                                                            at android.graphics.drawable.Drawable.invalidateSelf(Drawable.java:432)
                                                                            at android.graphics.drawable.Drawable.setVisible(Drawable.java:816)
                                                                            at android.view.View.setBackgroundDrawable(View.java:18160)
                                                                            at android.view.View.setBackground(View.java:18136)
                                                                            at android.view.View.setBackgroundResource(View.java:18119)
                                                                            at com.anilkrishna.baahubali2.MainActivity$1.run(MainActivity.java:30)
                                                                            at java.util.TimerThread.mainLoop(Timer.java:555)
                                                                            at java.util.TimerThread.run(Timer.java:505)

我的应用程序正在运行，正在显示第一张图像，该图像正在消失，然后停止运行。 问题出在if else循环上。 我无法弄清楚！

Answer 1

在UI线程的计时器内部执行代码，

protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_main);
            cl = (ConstraintLayout) findViewById(R.id.cl);
            cl.setBackgroundResource(R.drawable.bb1);
            i = 0;
            new Timer().scheduleAtFixedRate(new TimerTask() {
              @Override
              public void run() {
                runOnUiThread(new Runnable() {
                  @Override
                  public void run() {
                            cl.animate().alpha(0f).setDuration(1500);
                if (i == 0)
                  cl.setBackgroundResource(R.drawable.bb1);
                else if (i == 1)
                  cl.setBackgroundResource(R.drawable.bb2);
                else if (i == 2)
                  cl.setBackgroundResource(R.drawable.bb3);
                else if (i == 3)
                  cl.setBackgroundResource(R.drawable.bb4);
                else if (i == 4)
                  cl.setBackgroundResource(R.drawable.bb5);
                else if (i == 5)
                  cl.setBackgroundResource(R.drawable.bb6);
                i++;
                cl.animate().alpha(1f).setDuration(1500);
                  }
                });

              }
            }, 0, 3000);
          }