android开发----service下载图片

方法一：通过DownLoadService继承service类。如果在主线程中下载图片，会造成主线程的阻塞，所以需要在DownLoadService中创建线程，并且将数据传输到主线程，进行更新ui操作，那么android中那个知识点可以跨线程呢？答案就是Handler

MainActivity.java

package com.example.android_service_download;

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;

public class MainActivity extends Activity {
private Button button1;

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);

button1 = (Button) this.findViewById(R.id.button1);
button1.setOnClickListener(new OnClickListener() {

@Override
public void onClick(View v) {
Intent intent = new Intent(MainActivity.this, DownLoadService.class);
startService(intent);
}
});
}

@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;
}

@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();
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
}

DownLoadService.java

package com.example.android_service_download;

import java.io.ByteArrayOutputStream;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.URL;

import android.app.NotificationManager;
import android.app.Service;
import android.content.Intent;
import android.os.Handler;
import android.os.IBinder;
import android.os.Message;
import android.support.v4.app.NotificationCompat;
import android.widget.Toast;

public class DownLoadService extends Service {
private final String imagePath = "https://www.baidu.com/img/bd_logo1.png";
private NotificationCompat.Builder builder;
private NotificationManager manager;

private Handler handler = new Handler() {

public void handleMessage(android.os.Message msg) {
super.handleMessage(msg);
if (msg.what == 1) {
stopSelf();
Toast.makeText(getApplicationContext(), "下载完成！", Toast.LENGTH_SHORT).show();
}

builder.setProgress(100, msg.arg1, false);
manager.notify(1001, builder.build());
};
};

@Override
public void onCreate() {
super.onCreate();

manager = (NotificationManager) getSystemService(NOTIFICATION_SERVICE);
builder = new NotificationCompat.Builder(getApplicationContext());
builder.setSmallIcon(R.drawable.ic_launcher);
builder.setContentTitle("DownLoad");
builder.setContentText("downLoad...");
manager.notify(1001, builder.build());
}

/**
* 需要下载网络图片，下载完成需要停止service
*/
@Override
public int onStartCommand(Intent intent, int flags, int startId) {
new Thread(new MyTread()).start();
return super.onStartCommand(intent, flags, startId);
}

@Override
public void onDestroy() {
super.onDestroy();
}

@Override
public IBinder onBind(Intent intent) {
return null;
}

public class MyTread implements Runnable {
@Override
public void run() {
ByteArrayOutputStream stream = null;
try {
//建立连接
URL url = new URL(imagePath);
HttpURLConnection conn = (HttpURLConnection) url.openConnection();
conn.setRequestMethod("POST");

//连接
conn.connect();

//获取相应状态
if (conn.getResponseCode() == HttpURLConnection.HTTP_OK) {
/*InputStream is = conn.getInputStream();

Bitmap bitmap = BitmapFactory.decodeStream(is);
stream = new ByteArrayOutputStream();
bitmap.compress(Bitmap.CompressFormat.PNG, 100, stream);
byte[] byteArray = stream.toByteArray();

boolean flag = SDCardUtils.downLoadPicture(getApplicationContext(), "aa.png", byteArray);
if (flag) {
handler.sendEmptyMessage(1);
}*/

InputStream is1 = null;
stream = new ByteArrayOutputStream();
//获得文件中长度
int length = conn.getContentLength();
System.out.println("---->>"+length);
int sum_length = 0; //每次获取的大小
int len = 0;

byte[] data = new byte[1024];
try {
is1 = conn.getInputStream();
while ((len = is1.read(data)) > 0) {
stream.write(data, 0, len);
sum_length += len;

//计算每次下载文件大小的刻度
int value = (int) (sum_length/(float)length * 100);
Message message = Message.obtain();
message.arg1 = value;
handler.sendMessage(message);
}
if (SDCardUtils.downLoadPicture(getApplicationContext(), "123.png", stream.toByteArray())) {
handler.sendEmptyMessage(1);
}
} catch(Exception e) {
e.printStackTrace();
}
}

}catch (Exception e) {
e.printStackTrace();
} finally {
if(stream != null) {
try {
stream.close();
} catch(Exception e) {
e.printStackTrace();
}
}
}
}
}

}
SDCardUtils.java
package com.example.android_service_download;

import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;

import android.content.Context;

public class SDCardUtils {

public static boolean downLoadPicture(Context context, String name, byte[] buffer) {
boolean flag = false;
FileOutputStream outputStream = null;

try {
outputStream = context.getApplicationContext().openFileOutput(name, Context.MODE_PRIVATE);
outputStream.write(buffer, 0, buffer.length);
flag = true;
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} finally {
if (outputStream != null) {
try {
outputStream.close();
} catch(Exception e) {
e.printStackTrace();
}
}
}

return flag;
}
}


方法二：让DownLoadService继承IntentService，通过onHandleIntent方法来下载数据，原理就是对上述方法的封装
MainActivity.java

package com.example.android_service_intentservice;

import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;

import android.content.Context;

public class SDCardUtils {

public static b
a2b1
oolean downLoadPicture(Context context, String name, byte[] buffer) {
boolean flag = false;
FileOutputStream outputStream = null;

try {
outputStream = context.getApplicationContext().openFileOutput(name, Context.MODE_PRIVATE);
outputStream.write(buffer, 0, buffer.length);
flag = true;
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} finally {
if (outputStream != null) {
try {
outputStream.close();
} catch(Exception e) {
e.printStackTrace();
}
}
}

return flag;
}
}

DownLoadService.java

package com.example.android_service_intentservice;

import java.io.ByteArrayOutputStream;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.URL;

import android.app.IntentService;
import android.content.Intent;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;

public class DownLoadService extends IntentService {
private final String imagePath = "https://www.baidu.com/img/bd_logo1.png";

public DownLoadService() {
super("");
}

@Override
protected void onHandleIntent(Intent intent) {

ByteArrayOutputStream stream = null;
try {
//建立连接
URL url = new URL(imagePath);
HttpURLConnection conn = (HttpURLConnection) url.openConnection();
conn.setRequestMethod("POST");

//连接
conn.connect();

//获取相应状态
if (conn.getResponseCode() == HttpURLConnection.HTTP_OK) {
InputStream is = conn.getInputStream();

Bitmap bitmap = BitmapFactory.decodeStream(is);
stream = new ByteArrayOutputStream();
bitmap.compress(Bitmap.CompressFormat.PNG, 100, stream);
byte[] byteArray = stream.toByteArray();

boolean flag = SDCardUtils.downLoadPicture(getApplicationContext(), "aa.png", byteArray);
}

}catch (Exception e) {
e.printStackTrace();
} finally {
if(stream != null) {
try {
stream.close();
} catch(Exception e) {
e.printStackTrace();
}
}
}

}

}
SDCardUtils.java
package com.example.android_service_intentservice;

import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;

import android.content.Context;

public class SDCardUtils {

public static boolean downLoadPicture(Context context, String name, byte[] buffer) {
boolean flag = false;
FileOutputStream outputStream = null;

try {
outputStream = context.getApplicationContext().openFileOutput(name, Context.MODE_PRIVATE);
outputStream.write(buffer, 0, buffer.length);
flag = true;
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} finally {
if (outputStream != null) {
try {
outputStream.close();
} catch(Exception e) {
e.printStackTrace();
}
}
}

return flag;
}
}