安卓Handler跟Message_Android

安卓Handler和Message

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activity_main.xml

新窗口打开复制代码
<RelativeLayout?xmlns:android="http://schemas.android.com/apk/res/android"??
????xmlns:tools="http://schemas.android.com/tools"??
????android:layout_width="match_parent"??
????android:layout_height="match_parent"?>??
??
????<Button??
????????android:id="@+id/button1"??
????????android:layout_width="wrap_content"??
????????android:layout_height="wrap_content"??
????????android:layout_alignParentBottom="true"??
????????android:layout_centerHorizontal="true"??
????????android:text="下载网络图片"?/>??
??
????<ImageView??
????????android:id="@+id/imageView1"??
????????android:layout_width="wrap_content"??
????????android:layout_height="wrap_content"??
????????android:layout_centerHorizontal="true"??
????????android:layout_centerVertical="true"??
????????android:src="@drawable/ic_launcher"?/>??
??
</RelativeLayout>??

MainActivity

新窗口打开复制代码
package?com.example.android_asytask_download;??
??
import?java.io.ByteArrayOutputStream;??
import?java.io.InputStream;??
??
import?org.apache.http.HttpEntity;??
import?org.apache.http.HttpResponse;??
import?org.apache.http.client.HttpClient;??
import?org.apache.http.client.methods.HttpGet;??
import?org.apache.http.impl.client.DefaultHttpClient;??
import?org.apache.http.util.EntityUtils;??
??
import?android.os.AsyncTask;??
import?android.os.Bundle;??
import?android.os.Handler;??
import?android.os.Message;??
import?android.R.integer;??
import?android.app.Activity;??
import?android.app.ProgressDialog;??
import?android.content.Entity;??
import?android.graphics.Bitmap;??
import?android.graphics.BitmapFactory;??
import?android.view.Menu;??
import?android.view.View;??
import?android.widget.Button;??
import?android.widget.ImageView;??
??
public?class?MainActivity?extends?Activity?{??
????private?Button?button;??
????private?ImageView?imageView;??
????private?ProgressDialog?progressDialog;??
????private?final?int?IS_END?=?1;??
????private?String?image_path?=?"http://a.hiphotos.baidu.com/image/w%3D2048/sign=7610c70c5143fbf2c52ca1238446cb80/d4628535e5dde71120a3a1f2a5efce1b9d166145.jpg";??
????private?Handler?handler?=?new?Handler()?{??
????????@Override??
????????public?void?handleMessage(android.os.Message?msg)?{??
????????????byte[]?data?=?(byte[])?msg.obj;??
????????????Bitmap?bitmap?=?BitmapFactory.decodeByteArray(data,?0,?data.length);??
????????????imageView.setImageBitmap(bitmap);??
????????????if(msg.what==IS_END)??
????????????{??
????????????????progressDialog.dismiss();??
????????????}??
????????};??
????};??
??
????@Override??
????protected?void?onCreate(Bundle?savedInstanceState)?{??
????????super.onCreate(savedInstanceState);??
????????setContentView(R.layout.activity_main);??
??
????????button?=?(Button)?this.findViewById(R.id.button1);??
????????imageView?=?(ImageView)?this.findViewById(R.id.imageView1);??
????????progressDialog?=?new?ProgressDialog(this);??
????????progressDialog.setTitle("提示");??
????????progressDialog.setMessage("正在下载，请稍后...");??
????????progressDialog.setCancelable(false);//?点击不会失去焦点，直到下载结束??
??
????????button.setOnClickListener(new?View.OnClickListener()?{??
??
????????????@Override??
????????????public?void?onClick(View?arg0)?{??
????????????????//?TODO?Auto-generated?method?stub??
????????????????new?Thread(new?MyThread()).start();??
????????????????progressDialog.show();??
????????????}??
????????});??
????}??
??
????public?class?MyThread?implements?Runnable?{??
????????@Override??
????????public?void?run()?{??
????????????//?线程耗时部分的主体操作??
????????????HttpClient?httpClient?=?new?DefaultHttpClient();??
????????????HttpGet?httpGet?=?new?HttpGet(image_path);??
????????????try?{??
????????????????HttpResponse?httpResponse?=?httpClient.execute(httpGet);//?执行http操作??
????????????????if?(httpResponse.getStatusLine().getStatusCode()?==?200)?{??
????????????????????byte[]?data?=?EntityUtils.toByteArray(httpResponse??
????????????????????????????.getEntity());??
????????????????????//?一般实例化消息对象不用new?Message()，而是通过Message.obtain()??
????????????????????Message?message?=?Message.obtain();??
????????????????????message.obj?=?data;??
????????????????????message.what?=?IS_END;??
????????????????????handler.sendMessage(message);//?handler对象发送消息??
????????????????}??
????????????}?catch?(Exception?e)?{??
????????????????//?TODO:?handle?exception??
????????????}??
????????}??
????}??
??
????@Override??
????public?boolean?onCreateOptionsMenu(Menu?menu)?{??
????????//?Inflate?the?menu;?this?adds?items?to?the?action?bar?if?it?is?present.??
????????getMenuInflater().inflate(R.menu.main,?menu);??
????????return?true;??
????}??
??
}??

演示效果图片0 演示效果图片1 演示效果图片2

1.Handler对象负责发送消息和处理消息

2.Message消息对象实例化使用Message message = Message.obtain();