Activity01.java

package com.yarin.android.Examples_04_15;

import android.app.Activity;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.util.Log;
import android.widget.ImageView;
import android.widget.TextView;

public class Activity01 extends Activity {
    // ����ImageView����
    ImageView imageview;
    TextView textview;
    // ImageView��alphaֵ��
    int image_alpha = 255;

    Handler mHandler = new Handler();
    // �ؼ��߳�
    boolean isRun = false;

    /**
     * Called when the activity is first created.
     */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        isRun = true;

        // ���ImageView�Ķ���
        imageview = (ImageView) this.findViewById(R.id.ImageView01);
        textview = (TextView) this.findViewById(R.id.TextView01);

        // ����imageview��ͼƬ��Դ��ͬ��������xml����������������д
        // android:src="@drawable/logo"
//        imageview.setImageResource(R.drawable.logo);

        // ����imageview��Alphaֵ
        imageview.setAlpha(image_alpha);

        // ����һ���߳�����Alphaֵ�ݼ�
        new Thread(new Runnable() {
            public void run() {
                while (isRun) {
                    try {

                        Thread.sleep(200);
                        // ����Alphaֵ
                        updateAlpha();
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                }

            }
        }).start();

        // ������Ϣ֮�����imageview��ͼ
        mHandler = new Handler() {
            @Override
            public void handleMessage(Message msg) {
                Log.v(null, msg.toString());
                super.handleMessage(msg);
                imageview.setAlpha(image_alpha);
                textview.setText("����alphaֵ�ǣ�" + Integer.toString(image_alpha));
                // ����
                imageview.invalidate();
            }
        };
    }

    public void updateAlpha() {
        if (image_alpha - 7 >= 0) {
            image_alpha -= 7;
        } else {
            image_alpha = 0;
            isRun = false;
        }
        // ������Ҫ����imageview��ͼ����Ϣ
        mHandler.sendMessage(mHandler.obtainMessage());
    }
}