通過自定義視圖(Custom View)創建自定義按鈕(Custom Button)

前文描述過如何"建立自定義視圖", "通過XML調用自定義視圖", "處理自定義視圖的事件"和"調用invalidate()強制重繪View"等等. 自定義視圖也可以用來創建自定義按鈕.



修改main.xml添加三個自定義按鈕

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
  android:orientation="vertical"
  android:layout_width="fill_parent"
  android:layout_height="fill_parent"
  >
<TextView
  android:layout_width="fill_parent"
  android:layout_height="wrap_content"
  android:text="@string/hello"
  />
<com.AndroidCustomButton.MyButton
android:id="@+id/mybutton1"
  android:layout_width="wrap_content"
  android:layout_height="wrap_content"
  />
<com.AndroidCustomButton.MyButton
android:id="@+id/mybutton2"
  android:layout_width="fill_parent"
  android:layout_height="wrap_content"
  />
<com.AndroidCustomButton.MyButton
android:id="@+id/mybutton3"
  android:layout_width="fill_parent"
  android:layout_height="fill_parent"
  />
</LinearLayout>

擴展View類, 創建自定義按鈕, MyButton.java

package com.AndroidCustomButton;

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Rect;
import android.util.AttributeSet;
import android.view.View;

public class MyButton extends View {

private final int defaultImageRes = R.drawable.icon;
private Bitmap buttonBitmap;

public MyButton(Context context) {
super(context);
// TODO Auto-generated constructor stub
init(context);
}
public MyButton(Context context, AttributeSet attrs) {
super(context, attrs);
// TODO Auto-generated constructor stub

init(context);
}

public MyButton(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
// TODO Auto-generated constructor stub
init(context);
}

private void init(Context context){

/*
buttonBitmap = BitmapFactory.decodeResource(context.getResources(),
  getResources().getIdentifier(defaultImage, null, null));
  */

buttonBitmap = BitmapFactory.decodeResource(context.getResources(), defaultImageRes);

setBackgroundColor(Color.BLACK);
this.setFocusable(true);
this.setClickable(true);
}

int minWidth(){
return buttonBitmap.getWidth();
}

int minHeight(){
return buttonBitmap.getHeight();
}

@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {

      setMeasuredDimension(measureWidth(widthMeasureSpec), measureHeight(heightMeasureSpec));
  }

  private int measureWidth(int measureSpec) {
      int specMode = MeasureSpec.getMode(measureSpec);
      int specSize = MeasureSpec.getSize(measureSpec);

      if (specMode == MeasureSpec.EXACTLY) {
          // We were told how big to be
          return specSize;
      } else if (specMode == MeasureSpec.AT_MOST) {
          return Math.min(minWidth(), specSize);
      } else {
          return minWidth();
      }
  }

  private int measureHeight(int measureSpec) {
      int specMode = MeasureSpec.getMode(measureSpec);
      int specSize = MeasureSpec.getSize(measureSpec);

      if (specMode == MeasureSpec.EXACTLY) {
          // We were told how big to be
          return specSize;
      } else if (specMode == MeasureSpec.AT_MOST) {
       return Math.min(minHeight(), specSize);
      } else {
          return minHeight();
      }
  }



@Override
protected void onFocusChanged(boolean gainFocus, int direction,
 Rect previouslyFocusedRect) {
// TODO Auto-generated method stub
super.onFocusChanged(gainFocus, direction, previouslyFocusedRect);
if (gainFocus){
 setBackgroundColor(Color.GRAY);
}
else{
 setBackgroundColor(Color.BLACK);
}
}

@Override
protected void onDraw(Canvas canvas) {
// TODO Auto-generated method stub
Paint paint = new  Paint();
paint.setColor(Color.WHITE);
canvas.drawBitmap(buttonBitmap, 0, 0, paint);
}

}

修改主程式代碼

package com.AndroidCustomButton;

import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.widget.Toast;

public class AndroidCustomButton extends Activity {

  /** Called when the activity is first created. */
  @Override
  public void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      setContentView(R.layout.main);
    
      MyButton myButton1 = (MyButton)findViewById(R.id.mybutton1);
      MyButton myButton2 = (MyButton)findViewById(R.id.mybutton2);
      MyButton myButton3 = (MyButton)findViewById(R.id.mybutton3);
    
      myButton1.setOnClickListener(new MyButton.OnClickListener(){

 @Override
 public void onClick(View v) {
  // TODO Auto-generated method stub
  Toast.makeText(AndroidCustomButton.this, "myButton 1 Clicked", Toast.LENGTH_LONG).show();
 }});
    
      myButton2.setOnClickListener(new MyButton.OnClickListener(){

 @Override
 public void onClick(View v) {
  // TODO Auto-generated method stub
  Toast.makeText(AndroidCustomButton.this, "myButton 2 Clicked", Toast.LENGTH_LONG).show();
 }});
    
      myButton3.setOnClickListener(new MyButton.OnClickListener(){

 @Override
 public void onClick(View v) {
  // TODO Auto-generated method stub
  Toast.makeText(AndroidCustomButton.this, "myButton 3 Clicked", Toast.LENGTH_LONG).show();
 }});
    
  }
}