Android编程学习之Message处理Handler

来源：互联网发布：js 弧线编辑：程序博客网时间：2024/06/07 20:23

Android编程学习之Message处理Handler

1.实例化Handler对象，并重写void handleMessage(Message msg)方法：

Handler handler = new Handler(){    @Override    public void handleMessage(Message msg)    {        // TODO Auto-generated method stub        super.handleMessage(msg);        if(msg.what==1)        {            byte[] data  = (byte[]) msg.obj;            Bitmap bm = BitmapFactory.decodeByteArray(data, 0, data.length);            imageView.setImageBitmap(bm);        }    }};

2.在程序中定义并发送Message：

Message message = handler.obtainMessage();message.arg1=1;message.arg2=2;message.obj=data;message.what=1;handler.sendMessage(message);

也可以使用如下方法延迟10ms发送：

handler.sendMessageDelayed(handler.obtainMessage(int what,Object obj), 10);

例子1 android_handler_downloadimage MainActivity.java: ：

package com.example.android_handler_downloadimage;import java.io.IOException;import org.apache.http.HttpResponse;import org.apache.http.client.ClientProtocolException;import org.apache.http.client.HttpClient;import org.apache.http.client.methods.HttpPost;import org.apache.http.impl.client.DefaultHttpClient;import org.apache.http.util.EntityUtils;import android.os.Bundle;import android.os.Handler;import android.os.Message;import android.app.Activity;import android.app.ProgressDialog;import android.graphics.Bitmap;import android.graphics.BitmapFactory;import android.view.Menu;import android.view.View;import android.view.View.OnClickListener;import android.widget.Button;import android.widget.ImageView;public class MainActivity extends Activity{    private Button button;    private ImageView imageView;    private ProgressDialog dialog;    private int IS_COMPLETE = 0;    private static final String PATH = "http://10.0.2.2:8080/MyFirstWeb/mm.jpeg";    Handler handler = new Handler()    {        @Override        public void handleMessage(Message msg)        {            // TODO Auto-generated method stub            super.handleMessage(msg);            if (msg.what == 1)            {                byte[] data = (byte[]) msg.obj;                Bitmap bm = BitmapFactory.decodeByteArray(data, 0, data.length);                imageView.setImageBitmap(bm);                if (IS_COMPLETE == 1)                {                    dialog.dismiss();                }            }        }    };    @Override    protected void onCreate(Bundle savedInstanceState)    {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        imageView = (ImageView) this.findViewById(R.id.imageView1);        dialog = new ProgressDialog(this);        dialog.setTitle("提示");        dialog.setMessage("Loading...");        button = (Button) this.findViewById(R.id.button1);        button.setOnClickListener(new OnClickListener()        {            @Override            public void onClick(View arg0)            {                // TODO Auto-generated method stub                dialog.show();                new Thread(new MyThread()).start();            }        });    }    @Override    public boolean onCreateOptionsMenu(Menu menu)    {        // Inflate the menu; this adds items to the action bar if it is present.        getMenuInflater().inflate(R.menu.activity_main, menu);        return true;    }    class MyThread implements Runnable    {        @Override        public void run()        {            // TODO Auto-generated method stub            HttpClient httpClient = new DefaultHttpClient();            HttpPost httpPost = new HttpPost(PATH);            try            {                HttpResponse response = httpClient.execute(httpPost);                if (response.getStatusLine().getStatusCode() == 200)                {                    byte[] data = EntityUtils.toByteArray(response.getEntity());                    Message message = handler.obtainMessage();                    message.arg1 = 1;                    message.arg2 = 2;                    message.obj = data;                    message.what = 1;                    handler.sendMessage(message);                    IS_COMPLETE = 1;                }            }            catch (ClientProtocolException e)            {                // TODO Auto-generated catch block                e.printStackTrace();            }            catch (IOException e)            {                // TODO Auto-generated catch block                e.printStackTrace();            }            finally            {                httpClient.getConnectionManager().shutdown();            }        }    }}

例子2 android_handler_textview MainActivity.java:：

package com.example.android_handler_textview;import android.os.Bundle;import android.os.Handler;import android.os.Message;import android.app.Activity;import android.view.Menu;import android.view.View;import android.view.View.OnClickListener;import android.widget.Button;import android.widget.TextView;public class MainActivity extends Activity{    private Button button;    private TextView textView;    private MyHandler handler;    @Override    protected void onCreate(Bundle savedInstanceState)    {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        handler = new MyHandler();        textView = (TextView) this.findViewById(R.id.textView1);        button = (Button) this.findViewById(R.id.button1);        button.setOnClickListener(new OnClickListener()        {            @Override            public void onClick(View arg0)            {                // TODO Auto-generated method stub                new Thread(new MyThread()).start();            }        });    }    @Override    public boolean onCreateOptionsMenu(Menu menu)    {        // Inflate the menu; this adds items to the action bar if it is present.        getMenuInflater().inflate(R.menu.activity_main, menu);        return true;    }    class MyHandler extends Handler    {        @Override        public void handleMessage(Message msg)        {            // TODO Auto-generated method stub            super.handleMessage(msg);            textView.append((String) msg.obj + msg.arg1);        }    }    class MyThread implements Runnable    {        @Override        public void run()        {            // TODO Auto-generated method stub            int i = 1;            while (i <= 20)            {                try                {                    Thread.sleep(500);                }                catch (InterruptedException e)                {                    // TODO Auto-generated catch block                    e.printStackTrace();                }                Message message = handler.obtainMessage();                message.arg1 = i;                message.obj = "Tom";                i++;                handler.sendMessage(message);            }        }    }}

例子3 android_handler_progressdialog MainActivity.java:：

package com.example.android_handler_progressdialog;import android.os.Bundle;import android.os.Handler;import android.os.Message;import android.app.Activity;import android.app.ProgressDialog;import android.view.Menu;import android.view.View;import android.view.View.OnClickListener;import android.widget.Button;public class MainActivity extends Activity{    private Button button;    private ProgressDialog dialog;    private MyHandler handler;    @Override    protected void onCreate(Bundle savedInstanceState)    {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        handler = new MyHandler();        dialog = new ProgressDialog(this);        dialog.setTitle("下载进度");        dialog.setMessage("Loading...");        dialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);        button = (Button) this.findViewById(R.id.button1);        button.setOnClickListener(new OnClickListener()        {            @Override            public void onClick(View arg0)            {                // TODO Auto-generated method stub                dialog.show();                new Thread(new MyThread()).start();            }        });    }    @Override    public boolean onCreateOptionsMenu(Menu menu)    {        // Inflate the menu; this adds items to the action bar if it is present.        getMenuInflater().inflate(R.menu.activity_main, menu);        return true;    }    class MyHandler extends Handler    {        @Override        public void handleMessage(Message msg)        {            // TODO Auto-generated method stub            super.handleMessage(msg);            dialog.setProgress(msg.arg1);            dialog.setSecondaryProgress(msg.arg2);            if (msg.what == 1)            {                dialog.dismiss();            }        }    }    class MyThread implements Runnable    {        @Override        public void run()        {            // TODO Auto-generated method stub            int i = 0;            int k = 0;            while (i <= 100)            {                try                {                    Thread.sleep(50);                }                catch (InterruptedException e)                {                    // TODO Auto-generated catch block                    e.printStackTrace();                }                Message message = handler.obtainMessage();                message.arg1 = i;                message.arg2 = k + 10;                if (i == 100)                {                    message.what = 1;                }                handler.sendMessage(message);                i++;                k++;            }        }    }}

0 0