下载应用到SD卡并装配

下载应用到SD卡并安装
更新软件时要用到将软件下载到SD卡并主动弹出安装界面，就想安卓市场一样，下面总结一个简单的实训过程：
1、检测某个应用是否已经安装了：

public boolean isPkgInstalled(String packageName) {PackageManager pm = getPackageManager();try {pm.getPackageInfo(packageName, 0);} catch (Exception e) {return false;}return true;}

只需要一个包名就可以了。如果是更新软件本身就没必要检测安装，只检测版本号就可以了。

2、判断sd卡是否存在：

private boolean isSDcard() {if (android.os.Environment.getExternalStorageState().equals(android.os.Environment.MEDIA_MOUNTED)) {return true;} else {return false;}}

如果不存在就没必要下载了。

3、下载并保存到sd卡：

public void down_file(String url) {try {String path = "/sdcard/download/";filename = url.substring(url.lastIndexOf("/") + 1);URL myURL = new URL(url);URLConnection conn = myURL.openConnection();conn.connect();InputStream is = conn.getInputStream();fileSize = conn.getContentLength();if (fileSize <= 0)throw new RuntimeException(getString(R.string.download_unknow_size));if (is == null)throw new RuntimeException("stream is null");FileOutputStream fos = new FileOutputStream(path + filename);byte buf[] = new byte[1024];downLoadFileSize = 0;sendMsg(0);do {int numread = is.read(buf);if (numread == -1) {break;}fos.write(buf, 0, numread);downLoadFileSize += numread;sendMsg(1);} while (true);sendMsg(2);is.close();} catch (Exception ex) {Log.e("tag", "error: " + ex.getMessage(), ex);}}

4、等下载完成了就要启动安装界面：

private void installAPK() {String fileName = getSDPath() +"/download/"+filename;Intent intent = new Intent(Intent.ACTION_VIEW);intent.setDataAndType(Uri.fromFile(new File(fileName)), "application/vnd.android.package-archive");startActivity(intent);}

其中的sendMsg()方法是用于更新handler的。

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