安卓应用程序反复出现“Permission denied”错误提示

Question

我正在开发一款Android应用。该应用程序具有读取QR代码的功能（目前实现的唯一功能）。我使用Android Studio开发该应用程序。

当我将应用程序安装到我的Android手机上时，它显示“权限被拒绝”。 （已经为应用程序实现了请求权限，并且“Permission denied”是我在权限被拒绝的情况下放置在Android应用程序中的自定义消息）。

我可以手动给予该应用程序权限。当我这样做时，它会显示“权限已授予”，并在一秒钟内访问摄像头，但随后开始不断显示“权限被拒绝”的消息，摄像头视频流也消失了。

AndroidManifest.xml

    <?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.folio" >

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

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/AppTheme" >
        <activity android:name=".MainActivity" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest>

MainActivity.java

package com.example.folio;
import android.Manifest;
import android.app.AlertDialog;
import android.content.DialogInterface;
import android.content.Intent;
import android.content.pm.PackageManager;
import android.hardware.Camera;
import android.net.Uri;
import android.os.Build;
import android.support.v4.app.ActivityCompat;
import android.support.v4.content.ContextCompat;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.widget.Toast;


import com.google.zxing.Result;

import me.dm7.barcodescanner.zxing.ZXingScannerView;
//import sun.applet.Main;

public class MainActivity extends AppCompatActivity implements ZXingScannerView.ResultHandler {

    private static final int REQUEST_CAMERA=1;
    private ZXingScannerView scannerView;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        scannerView=new ZXingScannerView(this);
        setContentView(scannerView);

        if(Build.VERSION.SDK_INT >= Build.VERSION_CODES.M)
        {
            if(checkPermission())
            {
                Toast.makeText(MainActivity.this, "Permission granted!", Toast.LENGTH_LONG).show();
            }
            else
            {
                requestPermission();
            }
        }
    }

    private boolean checkPermission()
    {
        return (ContextCompat.checkSelfPermission(MainActivity.this, Manifest.permission.CAMERA)== PackageManager.PERMISSION_GRANTED);
    }
    private void requestPermission()
    {
        ActivityCompat.requestPermissions(this, new String[]{CAMERA_SERVICE}, REQUEST_CAMERA);
    }

    public void onRequestPermissionsResult(int requestCode, String permission[], int grantResults[])
    {
        switch(requestCode)
        {
            case REQUEST_CAMERA:
                if(grantResults.length>0)
                {
                    boolean cameraAccepted = grantResults[0] == PackageManager.PERMISSION_GRANTED;
                    if(cameraAccepted)
                    {
                        Toast.makeText(MainActivity.this, "Permission Granted!", Toast.LENGTH_LONG).show();
                    }
                    else
                    {
                        Toast.makeText(MainActivity.this, "Permission Denied!", Toast.LENGTH_LONG).show();
                        if(Build.VERSION.SDK_INT >= Build.VERSION_CODES.M)
                        {
                            if(shouldShowRequestPermissionRationale(CAMERA_SERVICE))
                            {
                                displayAlertMessage("Please allow access!", new DialogInterface.OnClickListener() {
                                    @Override
                                    public void onClick(DialogInterface dialog, int which) {
                                        requestPermissions(new String[]{CAMERA_SERVICE}, REQUEST_CAMERA);
                                    }
                                });
                                return;
                            }
                        }
                    }
                }
                break;
        }
    }
    @Override
    public void onResume()
    {
        super.onResume();
        if(Build.VERSION.SDK_INT >= Build.VERSION_CODES.M)
        {
            if(checkPermission())
            {
                if(scannerView==null)
                {
                    scannerView=new ZXingScannerView(this);
                    setContentView(scannerView);
                }
                scannerView.setResultHandler(this);
                scannerView.startCamera();
            }
            {
                requestPermission();
            }
        }
    }

    @Override
    public void onDestroy()
    {
        super.onDestroy();
        scannerView.stopCamera();
    }

    public void displayAlertMessage(String message, DialogInterface.OnClickListener listener)
    {
        new AlertDialog.Builder(MainActivity.this)
                .setMessage(message)
                .setPositiveButton("Ok", listener)
                .setNegativeButton("Cancel", null)
                .create()
                .show();
    }


    @Override
    public void handleResult(Result result) {
        final String scanResult=result.getText();
        AlertDialog.Builder builder=new AlertDialog.Builder(this);
        builder.setTitle("Scan result");
        builder.setPositiveButton("Ok", new DialogInterface.OnClickListener() {
            @Override
            public void onClick(DialogInterface dialog, int which) {
                scannerView.resumeCameraPreview(MainActivity.this);

            }
        });
        builder.setNeutralButton("Visit", new DialogInterface.OnClickListener() {
            @Override
            public void onClick(DialogInterface dialog, int which) {
                Intent intent = new Intent(Intent.ACTION_VIEW, Uri.parse(scanResult));
                startActivity(intent);

            }
        });
        builder.setMessage(scanResult);
        AlertDialog alert=builder.create();
        alert.show();
    }
}
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- IroCurie

---

哦。好的。如果可以的话让我把它移除掉。 - IroCurie

Answer 1

ActivityCompat.requestPermissions(this, new String[]{CAMERA_SERVICE}, REQUEST_CAMERA);

目前仍不清楚CAMERA_SERVICE是什么。然而，这应该是一组权限的数组，因此您很可能应该在此处使用Manifest.permission.CAMERA：

ActivityCompat.requestPermissions(this, new String[]{Manifest.permission.CAMERA}, REQUEST_CAMERA);

- CommonsWare

---

我做了这个，它起作用了。不再有权限被拒绝的问题。但是现在出现了一个新问题。它会重复地显示“已授权”，但屏幕上没有摄像头图像，只有一个闪烁的红色条纹。 - IroCurie

现在一切似乎都正常工作了。我在onResume()函数中漏掉了一个else。感谢大家的帮助。 - IroCurie

Answer 2

您的onResume()方法再次调用了requestPermission()，我认为您应该将其放在else条件中而不是直接调用它。

- Raghav Satyadev