Android 动态申请 REQUEST_INSTALL_PACKAGES 权限问题：申请权限失败

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

private static final int REQUEST_CODE_INSTALL_PERMISSION = 1;

ActivityResultLauncher<String> activityResultLauncher = registerForActivityResult(
        new ActivityResultContracts.RequestPermission(),
        isGranted -> {
            if (!isGranted) {
                Toast.makeText(this, "权限申请失败", Toast.LENGTH_SHORT).show();
                finish();
                return;
            }

            next();
        }
);

activityResultLauncher.launch(Manifest.permission.REQUEST_INSTALL_PACKAGES);

• 在 Android 开发中，执行上述权限申请的代码，权限申请失败

问题描述

1. Manifest.permission.REQUEST_INSTALL_PACKAGES 是一个特殊权限，不能通过常规的运行时权限请求方式（ActivityResultContracts.RequestPermission）来申请

2. Manifest.permission.REQUEST_INSTALL_PACKAGES 必须通过跳转到系统设置页面让用户手动授权

3. 正确的申请方式：检查是否已有权限，如果没有权限，引导用户前往系统设置

4. Manifest.permission.REQUEST_INSTALL_PACKAGES 在 Android 8.0 引入，低版本无需处理

处理策略

1. 在 AndroidManifest.xml 中声明权限

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

2. 跳转请求权限（过时写法）

private static final int REQUEST_CODE_INSTALL_PERMISSION = 1;

boolean canInstall = checkInstallPermission();

Log.i(TAG, "canInstall = " + canInstall);

if (!canInstall) {
    Intent intent = new Intent(Settings.ACTION_MANAGE_UNKNOWN_APP_SOURCES)
            .setData(Uri.parse("package:" + getPackageName()));
    startActivityForResult(intent, REQUEST_CODE_INSTALL_PERMISSION);
    return;
}

next();

private boolean checkInstallPermission() {
    return Build.VERSION.SDK_INT >= Build.VERSION_CODES.O ? getPackageManager().canRequestPackageInstalls() : true;
}

@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
    super.onActivityResult(requestCode, resultCode, data);

    if (requestCode == REQUEST_CODE_INSTALL_PERMISSION) {
        boolean canInstall = checkInstallPermission();

        Log.i(TAG, "now, canInstall = " + canInstall);

        if (!canInstall) {
            Toast.makeText(this, "权限申请失败", Toast.LENGTH_SHORT).show();
            return;
        }
        next();
    }
}

• 使用 ActivityResultLauncher 来替代（现代写法）

private boolean checkInstallPermission() {
    return Build.VERSION.SDK_INT >= Build.VERSION_CODES.O ? getPackageManager().canRequestPackageInstalls() : true;
}

boolean canInstall = checkInstallPermission();

Log.i(TAG, "canInstall = " + canInstall);

if (!canInstall) {
    ActivityResultLauncher<Intent> activityResultLauncher = registerForActivityResult(
            new ActivityResultContracts.StartActivityForResult(),
            result -> {
                boolean canInstall_ = checkInstallPermission();

                Log.i(TAG, "now, canInstall = " + canInstall_);

                if (!canInstall_) {
                    Toast.makeText(this, "权限申请失败", Toast.LENGTH_SHORT).show();
                    return;
                }
                next();
            }
    );

    Intent intent = new Intent(Settings.ACTION_MANAGE_UNKNOWN_APP_SOURCES)
            .setData(Uri.parse("package:" + getPackageName()));

    activityResultLauncher.launch(intent);

    return;
}
next();