学习目的：1.完整版下载示例 （@verride表示重写方法 无则是新建方法）
添加依赖1
compile 'com.squareup.okhttp3:okhttp:3.4.1'
定义一个回调接口（对下载过程中的各种状态进行监听和回调）
DownloadListenter1
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13public interface DownloadListener {
void onProgress(int progress);
void onSuccess();
void onFailed();
void onPaused();
void onCanceled();
}
AsynsTask实现下载功能1
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142//三个参数 传入数据 进度显示数据单位 反馈执行结果数据类型
public class DownloadTask extends AsyncTask<String, Integer, Integer> {
public static final int TYPE_SUCCESS = 0;
public static final int TYPE_FAILED = 1;
public static final int TYPE_PAUSED = 2;
public static final int TYPE_CANCELED = 3;
private DownloadListener listener;
private boolean isCanceled = false;
private boolean isPaused = false;
private int lastProgress;
public DownloadTask(DownloadListener listener) {
this.listener = listener;
}
//下载逻辑
protected Integer doInBackground(String... params) {
InputStream is = null;
RandomAccessFile savedFile = null;
File file = null;
try {
long downloadedLength = 0; // 记录已下载的文件长度
String downloadUrl = params[0];
String fileName = downloadUrl.substring(downloadUrl.lastIndexOf("/"));
String directory = Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS).getPath();
file = new File(directory + fileName);
if (file.exists()) {
downloadedLength = file.length();
}
long contentLength = getContentLength(downloadUrl);
if (contentLength == 0) {
return TYPE_FAILED;
} else if (contentLength == downloadedLength) {
// 已下载字节和文件总字节相等，说明已经下载完成了
return TYPE_SUCCESS;
}
OkHttpClient client = new OkHttpClient();
Request request = new Request.Builder()
// 断点下载，指定从哪个字节开始下载
.addHeader("RANGE", "bytes=" + downloadedLength + "-")
.url(downloadUrl)
.build();
Response response = client.newCall(request).execute();
if (response != null) {
is = response.body().byteStream();
savedFile = new RandomAccessFile(file, "rw");
savedFile.seek(downloadedLength); // 跳过已下载的字节
byte[] b = new byte[1024];
int total = 0;
int len;
while ((len = is.read(b)) != -1) {
if (isCanceled) {
return TYPE_CANCELED;
} else if(isPaused) {
return TYPE_PAUSED;
} else {
total += len;
savedFile.write(b, 0, len);
// 计算已下载的百分比
int progress = (int) ((total + downloadedLength) * 100 / contentLength);
publishProgress(progress);
}
}
response.body().close();
return TYPE_SUCCESS;
}
} catch (Exception e) {
e.printStackTrace();
} finally {
try {
if (is != null) {
is.close();
}
if (savedFile != null) {
savedFile.close();
}
if (isCanceled && file != null) {
file.delete();
}
} catch (Exception e) {
e.printStackTrace();
}
}
return TYPE_FAILED;
}
//界面显示当前下载进度
protected void onProgressUpdate(Integer... values) {
int progress = values[0];
if (progress > lastProgress) {
listener.onProgress(progress);
lastProgress = progress;
}
}
//通知最终下载结果
protected void onPostExecute(Integer status) {
switch (status) {
case TYPE_SUCCESS:
listener.onSuccess();
break;
case TYPE_FAILED:
listener.onFailed();
break;
case TYPE_PAUSED:
listener.onPaused();
break;
case TYPE_CANCELED:
listener.onCanceled();
default:
break;
}
}
public void pauseDownload() {
isPaused = true;
}
public void cancelDownload() {
isCanceled = true;
}
//获取下载文件总长度
private long getContentLength(String downloadUrl) throws IOException {
OkHttpClient client = new OkHttpClient();
Request request = new Request.Builder()
.url(downloadUrl)
.build();
Response response = client.newCall(request).execute();
if (response != null && response.isSuccessful()) {
long contentLength = response.body().contentLength();
response.close();
return contentLength;
}
return 0;
}
创建下载服务DownloadService（重写5个方法） DownloadBinder内部类（重写3个方法）两个类1
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112public class DownloadService extends Service {
private DownloadTask downloadTask;
private String downloadUrl;
private DownloadListener listener = new DownloadListener() {
public void onProgress(int progress) {
getNotificationManager().notify(1, getNotification("Downloading...", progress));
}
public void onSuccess() {
downloadTask = null;
// 下载成功时将前台服务通知关闭，并创建一个下载成功的通知
stopForeground(true);
getNotificationManager().notify(1, getNotification("Download Success", -1));
Toast.makeText(DownloadService.this, "Download Success", Toast.LENGTH_SHORT).show();
}
public void onFailed() {
downloadTask = null;
// 下载失败时将前台服务通知关闭，并创建一个下载失败的通知
stopForeground(true);
getNotificationManager().notify(1, getNotification("Download Failed", -1));
Toast.makeText(DownloadService.this, "Download Failed", Toast.LENGTH_SHORT).show();
}
public void onPaused() {
downloadTask = null;
Toast.makeText(DownloadService.this, "Paused", Toast.LENGTH_SHORT).show();
}
public void onCanceled() {
downloadTask = null;
stopForeground(true);
Toast.makeText(DownloadService.this, "Canceled", Toast.LENGTH_SHORT).show();
}
};
private DownloadBinder mBinder = new DownloadBinder();
public IBinder onBind(Intent intent) {
return mBinder;
}
class DownloadBinder extends Binder {
public void startDownload(String url) {
if (downloadTask == null) {
downloadUrl = url;
downloadTask = new DownloadTask(listener);
downloadTask.execute(downloadUrl);
startForeground(1, getNotification("Downloading...", 0));
Toast.makeText(DownloadService.this, "Downloading...", Toast.LENGTH_SHORT).show();
}
}
public void pauseDownload() {
if (downloadTask != null) {
downloadTask.pauseDownload();
}
}
public void cancelDownload() {
if (downloadTask != null) {
downloadTask.cancelDownload();
} else {
if (downloadUrl != null) {
// 取消下载时需将文件删除，并将通知关闭
String fileName = downloadUrl.substring(downloadUrl.lastIndexOf("/"));
String directory = Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS).getPath();
File file = new File(directory + fileName);
if (file.exists()) {
file.delete();
}
getNotificationManager().cancel(1);
stopForeground(true);
Toast.makeText(DownloadService.this, "Canceled", Toast.LENGTH_SHORT).show();
}
}
}
}
private NotificationManager getNotificationManager() {
return (NotificationManager) getSystemService(NOTIFICATION_SERVICE);
}
private Notification getNotification(String title, int progress) {
Intent intent = new Intent(this, MainActivity.class);
PendingIntent pi = PendingIntent.getActivity(this, 0, intent, 0);
NotificationCompat.Builder builder = new NotificationCompat.Builder(this);
builder.setSmallIcon(R.mipmap.ic_launcher);
builder.setLargeIcon(BitmapFactory.decodeResource(getResources(), R.mipmap.ic_launcher));
builder.setContentIntent(pi);
builder.setContentTitle(title);
if (progress >= 0) {
// 当progress大于或等于0时才需显示下载进度
builder.setContentText(progress + "%");
builder.setProgress(100, progress, false);
}
return builder.build();
}
}
MainActivity1
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76public class MainActivity extends AppCompatActivity implements View.OnClickListener{
private DownloadService.DownloadBinder downloadBinder;
private ServiceConnection connection = new ServiceConnection() {
public void onServiceDisconnected(ComponentName name) {
}
public void onServiceConnected(ComponentName name, IBinder service) {
downloadBinder = (DownloadService.DownloadBinder) service;
}
};
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Button startDownload = (Button) findViewById(R.id.start_download);
Button pauseDownload = (Button) findViewById(R.id.pause_download);
Button cancelDownload = (Button) findViewById(R.id.cancel_download);
startDownload.setOnClickListener(this);
pauseDownload.setOnClickListener(this);
cancelDownload.setOnClickListener(this);
Intent intent = new Intent(this, DownloadService.class);
startService(intent); // 启动服务
bindService(intent, connection, BIND_AUTO_CREATE); // 绑定服务
if (ContextCompat.checkSelfPermission(MainActivity.this, Manifest.permission.WRITE_EXTERNAL_STORAGE) != PackageManager.PERMISSION_GRANTED) {
ActivityCompat.requestPermissions(MainActivity.this, new String[]{ Manifest.permission. WRITE_EXTERNAL_STORAGE }, 1);
}
}
public void onClick(View v) {
if (downloadBinder == null) {
return;
}
switch (v.getId()) {
case R.id.start_download:
String url = "https://raw.githubusercontent.com/guolindev/eclipse/master/eclipse-inst-win64.exe";
downloadBinder.startDownload(url);
break;
case R.id.pause_download:
downloadBinder.pauseDownload();
break;
case R.id.cancel_download:
downloadBinder.cancelDownload();
break;
default:
break;
}
}
public void onRequestPermissionsResult(int requestCode, String[] permissions, int[] grantResults) {
switch (requestCode) {
case 1:
if (grantResults.length > 0 && grantResults[0] != PackageManager.PERMISSION_GRANTED) {
Toast.makeText(this, "拒绝权限将无法使用程序", Toast.LENGTH_SHORT).show();
finish();
}
break;
default:
}
}
protected void onDestroy() {
super.onDestroy();
unbindService(connection);
}
}
权限声明
<service
android:name=".DownloadService"
android:enabled="true"
android:exported="true" />