在这个例子中自定义了一个View，可以接受touch动作，然后在屏幕上即时的显示出touch的轨迹，类似于线条的屏幕上涂鸦。这个例子主要是演示如何将onTouchEvent与draw配合起来使用。在这个基础上，可以做很多有用的程序。
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Path;
import android.graphics.Paint.Style;
import android.view.MotionEvent;
import android.view.View;
/**
* Example for hand writing.
*
* @author ggg
* @version 2010/09/07
*
*/
public class HandwritingView extends View {
private Paint paint = null;
private Path path = null;
public HandwritingView(Context context) {
super(context);
path = new Path();
paint = new Paint();
paint.setColor(Color.YELLOW);
paint.setStyle(Style.STROKE);
paint.setAntiAlias(true);
this.setBackgroundColor(Color.BLACK);
}
@Override
public boolean onTouchEvent(MotionEvent event) {
if (event.getAction() == MotionEvent.ACTION_DOWN) {
int x = (int) event.getX();
int y = (int) event.getY();
path.moveTo(x, y);
invalidate();
return true;
} else if (event.getAction() == MotionEvent.ACTION_MOVE) {
int x = (int) event.getX();
int y = (int) event.getY();
path.lineTo(x, y);
invalidate();
return true;
}
return super.onTouchEvent(event);
}
@Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
if (path != null) {
canvas.drawPath(path, paint);
}
}
}
