Android AsyncTask Download
AndroidManifest.xml
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
activity_download_file.xml
<?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">
<Button
android:id="@+id/execute"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="@string/download"/>
<Button
android:id="@+id/cancel"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:enabled="false"
android:visibility="gone"
android:text="@string/cancel"/>
<ProgressBar
android:id="@+id/progress_bar"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:progress="0"
android:max="100"
style="?android:attr/progressBarStyleHorizontal"/>
<TextView
android:id="@+id/txtResult"
android:layout_width="fill_parent"
android:textSize="20dp"
android:layout_height="wrap_content"/>
<TextView
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:textSize="20dp"
android:text="@string/doneList"/>
<ScrollView
android:layout_width="fill_parent"
android:layout_height="wrap_content">
<TextView
android:id="@+id/txtDoneList"
android:textSize="20dp"
android:layout_width="fill_parent"
android:layout_height="wrap_content" />
</ScrollView>
</LinearLayout>
DownloadFileActivity
package com.buzz.activity;
import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.FileOutputStream;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.HttpStatus;
import org.apache.http.client.HttpClient;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.DefaultHttpClient;
import android.support.v7.app.ActionBarActivity;
import android.os.AsyncTask;
import android.os.Bundle;
import android.util.Log;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.Button;
import android.widget.ProgressBar;
import android.widget.TextView;
import com.buzz.models.action;
import com.buzz.utils.GlobalConst;
public class DownloadFileActivity extends ActionBarActivity {
static final String TAG = "ASYNC_TASK";
Button execute;
Button cancel;
ProgressBar progressBar;
TextView txtResult;
TextView txtDoneList;
Map<String, MyTask> taskList;
MyTask mTask;
MyApplication myApp;
int fileCounter;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_download_file);
myApp = (MyApplication) getApplication();
taskList = new HashMap<String, MyTask>();
execute = (Button) findViewById(R.id.execute);
execute.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
txtDoneList.setText("");
taskList.clear();
//注意每次需new一个实例,新建的任务只能执行一次,否则会出现异常
for (List<action> acList : myApp.actionList.values()) {
for (action ac : acList) {
taskList.put(ac.getServerpath(), new MyTask(ac.getClientpath(), ac.getFilename()));
}
}
for (Map.Entry<String, MyTask> entry : taskList.entrySet()) {
entry.getValue().execute(entry.getKey());
}
execute.setEnabled(false);
cancel.setEnabled(true);
}
});
cancel = (Button) findViewById(R.id.cancel);
cancel.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
//取消一个正在执行的任务,onCancelled方法将会被调用
mTask.cancel(true);
}
});
progressBar = (ProgressBar) findViewById(R.id.progress_bar);
txtResult = (TextView) findViewById(R.id.txtResult);
txtDoneList = (TextView) findViewById(R.id.txtDoneList);
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.menu_download_file, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
//noinspection SimplifiableIfStatement
return super.onOptionsItemSelected(item);
}
private class MyTask extends AsyncTask<String, Integer, String> {
//onPreExecute方法用于在执行后台任务前做一些UI操作
@Override
protected void onPreExecute() {
//Log.i(TAG, "onPreExecute() called");
txtResult.setText("准备下载...\n");
}
private String clientPath;
private String fileName;
protected MyTask(String clientPath, String fileName) {
this.clientPath = clientPath;
this.fileName = fileName;
}
//doInBackground方法内部执行后台任务,不可在此方法内修改UI
@Override
protected String doInBackground(String... params) {
//Log.i(TAG, "doInBackground(Params... params) called");
try {
HttpClient client = new DefaultHttpClient();
HttpGet get = new HttpGet(params[0]);
HttpResponse response = client.execute(get);
if (response.getStatusLine().getStatusCode() == HttpStatus.SC_OK) {
HttpEntity entity = response.getEntity();
InputStream is = entity.getContent();
long total = entity.getContentLength();
ByteArrayOutputStream baos = new ByteArrayOutputStream();
byte[] buf = new byte[1024];
int count = 0;
int length = -1;
while ((length = is.read(buf)) != -1) {
baos.write(buf, 0, length);
count += length;
//调用publishProgress公布进度,最后onProgressUpdate方法将被执行
publishProgress((int) ((count / (float) total) * 100));
//为了演示进度,休眠500毫秒
//Thread.sleep(500);
}
//保存文件
String filePath = GlobalConst.PATH_SDCARD + this.clientPath;
String fileName = this.fileName;
String saveTo = filePath + fileName;
File file = new File(filePath);
file.mkdirs();
file = null;
file = new File(saveTo);
file.createNewFile();
OutputStream outputStream = new FileOutputStream(file);
outputStream.write(baos.toByteArray());
baos.close();
baos.flush();
outputStream.close();
outputStream.flush();
file = null;
return "[" + this.fileName + "]" + "=>[下载完成]\n";
}
} catch (Exception e) {
//Log.i(TAG, e.getMessage());
}
return null;
}
//onProgressUpdate方法用于更新进度信息
@Override
protected void onProgressUpdate(Integer... progresses) {
//Log.i(TAG, "onProgressUpdate(Progress... progresses) called");
progressBar.setProgress(progresses[0]);
txtResult.setText("[" + this.fileName + "]" + "=>[下载中..." + progresses[0] + "%]\n");
}
//onPostExecute方法用于在执行完后台任务后更新UI,显示结果
@Override
protected void onPostExecute(String result) {
//Log.i(TAG, "onPostExecute(Result result) called");
txtResult.setText(result);
txtDoneList.append(result);
fileCounter++;
if (fileCounter == taskList.size()) {
execute.setEnabled(true);
cancel.setEnabled(false);
}
}
//onCancelled方法用于在取消执行中的任务时更改UI
@Override
protected void onCancelled() {
//Log.i(TAG, "onCancelled() called");
txtResult.setText("cancelled");
progressBar.setProgress(0);
execute.setEnabled(true);
cancel.setEnabled(false);
}
}
}