android动态添加图层

<pre name="code" class="java"><?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent" android:layout_height="fill_parent"
android:orientation="vertical">
<FrameLayout android:orientation="vertical"
android:layout_width="fill_parent" android:layout_height="0dip"
android:id="@+id/sc" android:scrollbars="horizontal"
android:layout_weight="1.0">
<ImageView android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:src="@drawable/image0"
/>
</FrameLayout>
<Button android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="Draw"
android:onClick="drawHandler"/>
<Button android:layout_width="fill_parent"
android:layout_height="wrap_content" android:text="Clear"
android:onClick="clearHandler"/>
</LinearLayout>

<pre name="code" class="java">package xyq.demo;

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.util.AttributeSet;
import android.view.View;
import android.view.ViewGroup.LayoutParams;
import android.widget.LinearLayout;

public class DrawView extends View {

public DrawView(Context context) {
super(context);
setLayoutParams(new LayoutParams(LinearLayout.LayoutParams.FILL_PARENT
,LinearLayout.LayoutParams.FILL_PARENT));
}

public DrawView(Context context, AttributeSet attrs) {
super(context, attrs);
}

@Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
Paint p = new Paint();
p.setColor(Color.RED);
p.setStrokeWidth(5);
canvas.drawLine(50, 50, 100, 150, p);
canvas.drawLine(100, 150, 20, 50, p);
}
}

<pre name="code" class="java">package xyq.demo;

import android.app.Activity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.FrameLayout;

public class MytesActivity extends Activity {
private FrameLayout container;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.draw_demo_layout);

container = (FrameLayout)findViewById(R.id.sc);
container.addView(new DrawView(this));
Log.v("test", ""+container.getChildCount());

}

public void drawHandler(View target){
container.addView(new DrawView(this));
Log.v("test", ""+container.getChildCount());
}

public void clearHandler(View target){
if(container.getChildCount() != 1){
container.removeViewAt(container.getChildCount()-1);
}
}
}