Android

Question

此代码用于测试应用程序是否有权限，检查后如果有权限则返回true，否则返回false。

但是当我运行应用程序停止工作时它不工作，所以我想知道为什么它不工作，如果代码中缺少某些东西：

EDIT2 - 根据建议进行了一些更正，但仍然无效：

 public class CheckPermission extends Activity {
    private final Context context;
    private static final String MNC = "MNC";
    int permReq = 0;
    String permMan = "";

    public CheckPermission(Context context) {
        this.context = context;
    }

    //perMan can be any code number higher than 0
    public void requestPermission(String permRequested){
        switch (permRequested) {
            case "CAMERA":
                //Request for Camera
                this.permReq =  ContextCompat.checkSelfPermission(context, Manifest.permission.CAMERA);
                this.permMan = Manifest.permission.CAMERA;
                break;
            case "INTERNET":
                //Requesr for Internet
                this.permReq =  ContextCompat.checkSelfPermission(context, Manifest.permission.INTERNET);
                this.permMan = Manifest.permission.INTERNET;
                break;
            case "STORAGE":
                //Request for group Storage - Read_External_Storage & Write_External_Storage
                this.permReq =  ContextCompat.checkSelfPermission(context, Manifest.permission_group.STORAGE);
                this.permMan = Manifest.permission_group.STORAGE;
                break;
            case "MICROPHONE":
                //Request for group Microphone - Record_Audio
                this.permReq =  ContextCompat.checkSelfPermission(context, Manifest.permission_group.MICROPHONE);
                this.permMan = Manifest.permission_group.MICROPHONE;
                break;
            case "LOCATION":
                //Request for group Location - Acess_Fine_Location & Acess_Coarse_Location
                this.permReq =  ContextCompat.checkSelfPermission(context, Manifest.permission_group.LOCATION);
                this.permMan = Manifest.permission_group.LOCATION;
                break;
            case "CALL":
                //Requesr for call
                this.permReq = ContextCompat.checkSelfPermission(context, Manifest.permission.CALL_PHONE);
                this.permMan = Manifest.permission.CALL_PHONE;
                break;
            default:
                break;
        }
    }

    public boolean hasPermission( String permRequested){
        final PackageManager pm = context.getPackageManager();

        if(isMNC_Or_Higher()) {
            requestPermission(permRequested);
            Toast.makeText(this.context, "Is MNC - permMan: " + this.permMan + " Perm required: " + permReq, Toast.LENGTH_SHORT).show();

            if (permReq != pm.PERMISSION_GRANTED) {
                ActivityCompat.requestPermissions(this, new String[]{this.permMan}, this.permReq);
                return false;
            }
        }
        return true;
    }

    //check if is 6.0 or higher
    public boolean isMNC_Or_Higher(){
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
            return true;
        }
        return false;
    }

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

        if (requestCode == this.permReq) {
            if (grantResults.length == 1 &&
                    grantResults[0] == PackageManager.PERMISSION_GRANTED) {
                Toast.makeText(this, "Permissão concedida", Toast.LENGTH_SHORT).show();
            } else {
                Toast.makeText(this, "Permissão negada", Toast.LENGTH_SHORT).show();
            }
        } else {
            super.onRequestPermissionsResult(requestCode, permissions, grantResults);
        }
    }
}

错误：

PID：25504 java.lang.NullPointerException: 尝试在空对象引用上调用虚方法 'android.content.Context android.content.Context.getApplicationContext()' 在 android.content.ContextWrapper.getApplicationContext(ContextWrapper.java:107) 在 com.dev.kamui.patrulhacomunitaria.CheckPermission.hasPermission(CheckPermission.java:68) 在 com.dev.kamui.patrulhacomunitaria.Pagina_Principal$1.onClick(Pagina_Principal.java:47) 在 android.view.View.performClick(View.java:5198) 在 android.view.View$PerformClick.run(View.java:21147) 在 android.os.Handler.handleCallback(Handler.java:739) 在 android.os.Handler.dispatchMessage(Handler.java:95) 在 android.os.Looper.loop(Looper.java:148) 在 android.app.ActivityThread.main(ActivityThread.java:5417) 在 java.lang.reflect.Method.invoke（本机方法）在 com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726) 在 com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)

Answer 1

requestPermissions 需要这样调用

requestPermissions(this, new String[]{this.permMan}, this.permReq);

如果您希望将 CheckPermission 用作 Util class，则无需从 Activity class 继承它。也不需要在 CheckPermission 构造函数中执行 "this.context = context;" 。而是通过 hasPermission 方法将上下文发送到 requestPermission 方法。也在 ActivityCompat.requestPermissions 中使用它。然后在每个调用 hasPermission 的 activity 中实现 onRequestPermissionsResult。

Answer 2

Activity 不应该有你写的这样的构造函数。

Activity 本身是 context 的子类，所以你可以写 this 而不是 context:

this.permReq = ContextCompat.checkSelfPermission(this, Manifest.permission_group.STORAGE);

Answer 3

从 Android 6.0 及更高版本开始，您必须在代码中请求许可。

private static final int PERMISSION_REQUEST_CODE = 1;

if (android.os.Build.VERSION.SDK_INT >= android.os.Build.VERSION_CODES.M) {

    if (checkSelfPermission(Manifest.permission.SEND_SMS)
            == PackageManager.PERMISSION_DENIED) {

        Log.d("permission", "permission denied to SEND_SMS - requesting it");
        String[] permissions = {Manifest.permission.SEND_SMS};

        requestPermissions(permissions, PERMISSION_REQUEST_CODE);

    }
}

Android - 检查权限

Android - Check Permission

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