startactivityforresult与权限请求的结合

startActivityForResult和权限请求可以结合使用，以便在启动新活动之前检查并请求必要的权限。以下是一个简单的示例，说明如何实现这种结合：

1. 首先，确保在AndroidManifest.xml文件中添加了所需的权限：

<uses-permission android:name="android.permission.CAMERA" />
<uses-feature android:name="android.hardware.camera" android:required="true" />

2. 在启动新活动之前，检查并请求相机权限（如果尚未授权）：

private static final int REQUEST_CODE_PERMISSIONS = 100;

private void launchActivityWithPermissionCheck() {
    if (ContextCompat.checkSelfPermission(this, Manifest.permission.CAMERA) != PackageManager.PERMISSION_GRANTED) {
        ActivityCompat.requestPermissions(this, new String[]{Manifest.permission.CAMERA}, REQUEST_CODE_PERMISSIONS);
    } else {
        launchActivity();
    }
}

3. 定义launchActivity()方法以启动新活动：

private void launchActivity() {
    Intent intent = new Intent(this, TargetActivity.class);
    startActivityForResult(intent, REQUEST_CODE_PERMISSIONS);
}

4. 重写onRequestPermissionsResult()方法以处理权限请求结果：

@Override
public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
    super.onRequestPermissionsResult(requestCode, permissions, grantResults);

    if (requestCode == REQUEST_CODE_PERMISSIONS) {
        if (grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
            // Permission granted, you can launch the activity now
            launchActivity();
        } else {
            // Permission denied, inform the user
            Toast.makeText(this, "Camera permission is required to launch the target activity", Toast.LENGTH_SHORT).show();
        }
    }
}

5. 在TargetActivity中处理结果，并将结果返回给启动它的活动：

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

    if (requestCode == REQUEST_CODE_PERMISSIONS && resultCode == RESULT_OK) {
        // Permission granted, you can process the result now
        // ...
    } else {
        // Permission denied or activity finished, inform the caller activity
        setResult(RESULT_CANCELED);
        finish();
    }
}

现在，在启动TargetActivity之前，系统会检查并请求相机权限。如果用户授权了权限，活动将正常启动；否则，将显示一条消息通知用户需要权限。