自定义view

1. 此程式執行時，呈現如下的畫面：
2. 左邊的圖形就是自行定義的DrawView 之呈現。按下右邊的RadioButton 之
後，DrawView 物件就會以不同顏色重新繪圖，如下：
3. 再按下RadioButton 之後，DrawView 物件就再以不同顏色重新繪圖。
public class ex10 extends Activity implements OnClickListener {
/** Called when the activity is first created. */
private final int WC = ViewGroup.LayoutParams.WRAP_CONTENT;
DrawView dv;
@Override
public void onCreate(Bundle icicle) {
super.onCreate(icicle);
LinearLayout layout = new LinearLayout(this);
layout.setOrientation(LinearLayout.HORIZONTAL);
LinearLayout.LayoutParams param =
new LinearLayout.LayoutParams(150, 300);
param.leftMargin = 1;
dv = new DrawView(this);
layout.addView(dv, param);
RadioButton ra;
ra = new RadioButton(this);
param = new LinearLayout.LayoutParams(WC, WC);
param.topMargin = 40;
layout.addView(ra, param);
ra.setOnClickListener(this);
setContentView(layout);
}
public void onClick(View arg0)
{ dv.invalidate(); }
}
// ---- DrawView.java 程式碼 -------------------------------------
package com.misoo.ex10;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.view.View;
public class DrawView extends View {
private Paint pa = new Paint();
private boolean yn = false;
public DrawView(Context context) {
super(context);
}
@Override
protected void onDraw(Canvas canvas) {
yn = !yn;
if(yn) pa.setColor(Color.GRAY);
else pa.setColor(Color.WHITE);
canvas.drawRect(10, 10, 100, 100, pa);
pa.setColor(Color.YELLOW);
if(yn) pa.setColor(Color.YELLOW);
else pa.setColor(Color.BLUE);
pa.setStrokeWidth(4);
pa.setStrokeCap(Paint.Cap.ROUND);
canvas.drawLine(10, 55, 100, 55, pa);
canvas.drawLine(55, 10, 55, 100, pa);
pa.setColor(Color.RED);
canvas.drawRect(50, 50, 60, 60, pa);
}
}