下载并保存文件

public void downloadUpdateFile(String downloadUrl, String saveFile) throws Exception {

int bytesum = 0;
    int byteread = 0;
    URL url = new URL(downloadUrl);


    try {
        URLConnection conn = url.openConnection();
        InputStream inStream = conn.getInputStream();
        File file = new File("/data/data/com.example.updatetest/files/"+saveFile);
        Runtime.getRuntime().exec("chmod 777 "+ file);
        FileOutputStream fs = new FileOutputStream(file);
        //getApplicationContext().openFileOutput(saveFile, getApplicationContext().MODE_APPEND);


        byte[] buffer = new byte[1204];
        int length;
        while ((byteread = inStream.read(buffer)) != -1) {
            bytesum += byteread;
            System.out.println(bytesum);
            fs.write(buffer, 0, byteread);
        }
        installApk();
        
    } catch (FileNotFoundException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();

    }}

public void installApk(){
Intent i = new Intent(Intent.ACTION_VIEW); 
String filePath = "/data/data/com.example.updatetest/files/ModuleTest.apk"; 
i.setDataAndType(Uri.parse("file://" + filePath),"application/vnd.android.package-archive"); 
// i.setDataAndType(
// Uri.parse("file:///data/data/com.example.updatetest/files/yuehe.mpg"),
// "video/mp4");
i.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
startActivity(i); 
}

记得加上网络和读写的权限:

<uses-permission android:name="android.permission.INTERNET"/>  
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
<uses-permission android:name="android.permission.INSTALL_PACKAGES"/>
<uses-permission android:name="android.permission.GET_TASKS"/> 

<uses-permission android:name="android.permission.INSTALL_LOCATION_PROVIDER"/>