set file read permission to file in android

I am writing an app which downloads an *.apk from a url and then tries to install it. It appears I am running into Permission denied error when trying 开发者_开发问答to get PackageManager to install it. I want set the permission of the file to readable from java code. How do you do this.

Here is how I am reading the file

InputStream input = new BufferedInputStream(url.openStream());
 OutputStream output = new FileOutputStream(PATH + fileName);

 byte data[] = new byte[1024];


 int count;

while((count = input.read(data)) != -1) {
                total += count;
                output.write(data, 0, count);
}

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You can't install .apk files directly using PackageManager. Only system applications can do this.

But you can ask system to install application using standard installation workflow. Here is an example:

Intent intent = new Intent(Intent.ACTION_VIEW);
Uri uri = Uri.fromFile(new File(pathToApk));
intent.setDataAndType(uri, "application/vnd.android.package-archive");
startActivity(intent);

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This all assuming you actually succeeded downloading the .apk. But if you failed at that step, you should check your WRITE_EXTERNAL_STORAGE permission. And also check that your sdcard is not shared via USB (if so, your application will not have write permission to sdcard).

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if you want to change file permissions on android 2.2 and higher you can use this:

Runtime.getRuntime().exec("chmod 777 " + PATH + fileName);

in android 3 you can do it also without using a native code workaround:

new java.io.File(PATH + fileName).setReadable(true, false);

---

I haven't tried exactly what is being asked here, but this will change a files permissions in any version of android:

exec("chmod 0777 " + fileOfInterest.getAbsolutePath());  //whatever permissions you require

private void exec(String command) {
    Runtime runtime = Runtime.getRuntime();
    Process process;
    try {
        process = runtime.exec(command);
        try {
            String str;
            process.waitFor();
            BufferedReader stdError = new BufferedReader(new InputStreamReader(process.getErrorStream()));
            while ((str = stdError.readLine()) != null) {
                Log.e("Exec",str);
                mErrOcc = true;  //I use this elsewhere to determine if an error was encountered
            }
            process.getInputStream().close();
            process.getOutputStream().close();
            process.getErrorStream().close();
        } catch (InterruptedException e) {
            mErrOcc = true;
        }
    } catch (IOException e1) {
        mErrOcc = true;
    }
}

This is like what Shmuel was suggesting, but more complete and btw, what he suggested does work in 1.5 and higher, not 2.2 and higher.