Use of invalidate() in using View while creating animation

Question

When I create an application, that uses View to create basic animation, the use of invalidate kind of loops it again and again to give a continuous animation. But, while using SurfaceView, the use of invalidate gives an error. Can someone help me out with it?

package com.example.newapplication;

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.view.SurfaceHolder;
import android.view.SurfaceView;

public class SurfaceAnimation extends SurfaceView implements Runnable{


    SurfaceHolder ourHolder;
    Thread ourThread = null;
    boolean isRunning = true;

    public SurfaceAnimation(Context context) {
        super(context);
        // TODO Auto-generated constructor stub
        ourHolder = getHolder();
        ourThread = new Thread(this);
        ourThread.start();

    }

    @Override
    public void run() {
        // TODO Auto-generated method stub
        while(isRunning){
            if(!ourHolder.getSurface().isValid())
                continue;
            else{
                Canvas canvas = ourHolder.lockCanvas();
                canvas.drawColor(Color.CYAN);
                ourHolder.unlockCanvasAndPost(canvas);
//              invalidate();
                }

        }


    } 

}

The logcat for above is:

05-30 04:41:47.240: E/AndroidRuntime(1869): FATAL EXCEPTION: Thread-120
05-30 04:41:47.240: E/AndroidRuntime(1869): Process: com.example.newapplication, PID: 1869
05-30 04:41:47.240: E/AndroidRuntime(1869): android.view.ViewRootImpl$CalledFromWrongThreadException: Only the original thread that created a view hierarchy can touch its views.
05-30 04:41:47.240: E/AndroidRuntime(1869):     at android.view.ViewRootImpl.checkThread(ViewRootImpl.java:6094)
05-30 04:41:47.240: E/AndroidRuntime(1869):     at android.view.ViewRootImpl.invalidateChildInParent(ViewRootImpl.java:857)
05-30 04:41:47.240: E/AndroidRuntime(1869):     at android.view.ViewGroup.invalidateChild(ViewGroup.java:4320)
05-30 04:41:47.240: E/AndroidRuntime(1869):     at android.view.View.invalidate(View.java:10935)
05-30 04:41:47.240: E/AndroidRuntime(1869):     at android.view.View.invalidate(View.java:10890)
05-30 04:41:47.240: E/AndroidRuntime(1869):     at com.example.newapplication.SurfaceAnimation.run(SurfaceAnimation.java:35)
05-30 04:41:47.240: E/AndroidRuntime(1869):     at java.lang.Thread.run(Thread.java:841)

Answer 1

You have to use postInvalidate() instead of invalidate() if you want to update a view from non-ui thread. That is what your logcat says:

Only the original thread that created a view hierarchy can touch its views.