如何在 Android 应用程序中请求权限？

从Android 6.0 (API 23)开始，用户在安装时无需请求权限，开发人员需要在运行时请求权限。在运行时只能请求清单文件中定义的权限。

权限类型

1. 安装时权限：如果是Android 5.1.1 (API 22) 或更低版本，在安装时在Google Play Store请求权限。

如果用户接受权限，则安装应用程序。否则应用程序安装被取消。

2. Run-Time Permissions：如果是Android 6 (API 23) 或更高版本，则在应用程序运行期间的运行时请求权限。

如果用户接受权限，则可以使用应用程序的该功能。否则要使用该功能，应用程序会再次请求权限。

因此，现在在运行时请求权限。在本文中，我们将讨论如何在运行时在 Android 应用程序中请求权限。

在运行时请求权限的步骤

第 1 步：在Android Manifest 文件中声明权限：在 Android 中，使用uses-permission标签在AndroidManifest.xml文件中声明权限。

在这里，我们声明存储和相机权限。

第二步：修改activity_main.xml文件，添加两个按钮来请求按钮点击权限：权限将被检查并在按钮点击时请求。打开activity_main.xml文件并向其中添加两个按钮。

第 3 步：检查是否已授予权限。如果尚未授予权限，请向用户请求权限：要使用任何服务或功能，都需要权限。因此，我们必须确保为此授予权限。如果不是，则请求权限。

检查权限：从 Android 6.0（API 级别 23）开始，用户有权随时撤销任何应用程序的权限，即使该应用程序的目标 API 级别较低。因此，要使用该服务，应用程序每次都需要检查权限。

句法：

if(ContextCompat.checkSelfPermission(thisActivity, Manifest.permission.WRITE_CALENDAR)
   != PackageManager.PERMISSION_GRANTED) 
{
    // Permission is not granted
}

请求权限：当上述语法中的checkSelfPermission()方法返回PERMISSION_DENIED时，我们需要提示用户该权限。 Android 提供了几种可用于请求权限的方法，例如requestPermissions() 。

句法：

ActivityCompat.requestPermissions(MainActivity.this, 
                                  permissionArray, 
                                  requestCode);

Here permissionArray is an array of type String.

例子：

Java

// Function to check and request permission
public void checkPermission(String permission, int requestCode)
{
    // Checking if permission is not granted
    if (ContextCompat.checkSelfPermission(MainActivity.this, permission) == PackageManager.PERMISSION_DENIED) {
        ActivityCompat.requestPermissions(MainActivity.this, new String[] { permission }, requestCode);
    }
    else {
        Toast.makeText(MainActivity.this, "Permission already granted", Toast.LENGTH_SHORT).show();
    }
}

科特林

// Function to check and request permission.
private fun checkPermission(permission: String, requestCode: Int) {
        if (ContextCompat.checkSelfPermission(this@MainActivity, permission) == PackageManager.PERMISSION_DENIED) {
            // Requesting the permission
            ActivityCompat.requestPermissions(this@MainActivity, arrayOf(permission), requestCode)
        } else {
            Toast.makeText(this@MainActivity, "Permission already granted", Toast.LENGTH_SHORT).show()
        }
   }

如果已授予权限，此函数将显示 Toast 消息，否则提示用户授予权限。

第 4 步：覆盖 onRequestPermissionsResult() 方法：在用户授予或拒绝权限时调用onRequestPermissionsResult() 。 RequestCode是该函数的参数之一，用于检查用户对相应请求的操作。这里显示了一条 toast 消息，指示权限和用户操作。

例子：

Java

// This function is called when user accept or decline the permission.
// Request Code is used to check which permission called this function.
// This request code is provided when user is prompt for permission.
@Override
public void onRequestPermissionsResult(int requestCode,
                                       @NonNull String[] permissions,
                                       @NonNull int[] grantResults)
{
    super.onRequestPermissionsResult(requestCode, permissions, grantResults);
   
    if (requestCode == CAMERA_PERMISSION_CODE) {
 
        // Checking whether user granted the permission or not.
        if (grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
 
            // Showing the toast message
            Toast.makeText(MainActivity.this, "Camera Permission Granted", Toast.LENGTH_SHORT).show();
        }
        else {
            Toast.makeText(MainActivity.this, "Camera Permission Denied", Toast.LENGTH_SHORT).show();
        }
    }
    else if (requestCode == STORAGE_PERMISSION_CODE) {
        if (grantResults.length > 0
            && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
            Toast.makeText(MainActivity.this, "Storage Permission Granted", Toast.LENGTH_SHORT).show();
        }
        else {
            Toast.makeText(MainActivity.this, "Storage Permission Denied", Toast.LENGTH_SHORT).show();
        }
    }
}

科特林

// This function is called when the user accepts or decline the permission.
// Request Code is used to check which permission called this function.
// This request code is provided when the user is prompt for permission.
override fun onRequestPermissionsResult(requestCode: Int,
                                        permissions: Array,
                                        grantResults: IntArray) {
        super.onRequestPermissionsResult(requestCode, permissions, grantResults)
        if (requestCode == CAMERA_PERMISSION_CODE) {
            if (grantResults.isNotEmpty() && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
                Toast.makeText(this@MainActivity, "Camera Permission Granted", Toast.LENGTH_SHORT).show()
            } else {
                Toast.makeText(this@MainActivity, "Camera Permission Denied", Toast.LENGTH_SHORT).show()
            }
        } else if (requestCode == STORAGE_PERMISSION_CODE) {
            if (grantResults.isNotEmpty() && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
                Toast.makeText(this@MainActivity, "Storage Permission Granted", Toast.LENGTH_SHORT).show()
            } else {
                Toast.makeText(this@MainActivity, "Storage Permission Denied", Toast.LENGTH_SHORT).show()
            }
     }
}

下面是这个应用程序的完整代码：

下面是activity_main.xml文件的代码。

下面是AndroidManifest.xml文件的代码。

下面是MainActivity文件的代码。

科特林

import android.Manifest
import android.content.pm.PackageManager
import android.os.Bundle
import android.widget.Button
import android.widget.Toast
import androidx.appcompat.app.AppCompatActivity
import androidx.core.app.ActivityCompat
import androidx.core.content.ContextCompat
 
class MainActivity : AppCompatActivity() {
 
    companion object {
        private const val CAMERA_PERMISSION_CODE = 100
        private const val STORAGE_PERMISSION_CODE = 101
    }
 
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
 
        // Defining Buttons
        val storage: Button? = findViewById(R.id.storage)
        val camera: Button? = findViewById(R.id.camera)
 
        // Set Buttons on Click Listeners
        storage?.setOnClickListener {checkPermission(
                    Manifest.permission.WRITE_EXTERNAL_STORAGE,
                    STORAGE_PERMISSION_CODE)
        }
        camera?.setOnClickListener {
            checkPermission(Manifest.permission.CAMERA,
                    CAMERA_PERMISSION_CODE)
        }
    }
 
    // Function to check and request permission.
    private fun checkPermission(permission: String, requestCode: Int) {
        if (ContextCompat.checkSelfPermission(this@MainActivity, permission) == PackageManager.PERMISSION_DENIED) {
 
            // Requesting the permission
            ActivityCompat.requestPermissions(this@MainActivity, arrayOf(permission), requestCode)
        } else {
            Toast.makeText(this@MainActivity, "Permission already granted", Toast.LENGTH_SHORT).show()
        }
    }
 
    // This function is called when the user accepts or decline the permission.
    // Request Code is used to check which permission called this function.
    // This request code is provided when the user is prompt for permission.
    override fun onRequestPermissionsResult(requestCode: Int,
                                            permissions: Array,
                                            grantResults: IntArray) {
        super.onRequestPermissionsResult(requestCode, permissions, grantResults)
        if (requestCode == CAMERA_PERMISSION_CODE) {
            if (grantResults.isNotEmpty() && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
                Toast.makeText(this@MainActivity, "Camera Permission Granted", Toast.LENGTH_SHORT).show()
            } else {
                Toast.makeText(this@MainActivity, "Camera Permission Denied", Toast.LENGTH_SHORT).show()
            }
        } else if (requestCode == STORAGE_PERMISSION_CODE) {
            if (grantResults.isNotEmpty() && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
                Toast.makeText(this@MainActivity, "Storage Permission Granted", Toast.LENGTH_SHORT).show()
            } else {
                Toast.makeText(this@MainActivity, "Storage Permission Denied", Toast.LENGTH_SHORT).show()
            }
        }
    }
}

Java

import android.Manifest;
import android.content.pm.PackageManager;
import android.support.annotation.NonNull;
import android.support.v4.app.ActivityCompat;
import android.support.v4.content.ContextCompat;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.Toast;
 
public class MainActivity extends AppCompatActivity {
 
    // Defining Buttons
    private Button storage, camera;
 
    // Defining Permission codes.
    // We can give any value
    // but unique for each permission.
    private static final int CAMERA_PERMISSION_CODE = 100;
    private static final int STORAGE_PERMISSION_CODE = 101;
 
    @Override
    protected void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
 
        storage = findViewById(R.id.storage);
        camera = findViewById(R.id.camera);
 
        // Set Buttons on Click Listeners
        storage.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v)
            {
                checkPermission(Manifest.permission.WRITE_EXTERNAL_STORAGE, STORAGE_PERMISSION_CODE);
            }
        });
 
        camera.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v)
            {
                checkPermission(Manifest.permission.CAMERA, CAMERA_PERMISSION_CODE);
            }
        });
    }
 
    // Function to check and request permission.
    public void checkPermission(String permission, int requestCode)
    {
        if (ContextCompat.checkSelfPermission(MainActivity.this, permission) == PackageManager.PERMISSION_DENIED) {
 
            // Requesting the permission
            ActivityCompat.requestPermissions(MainActivity.this, new String[] { permission }, requestCode);
        }
        else {
            Toast.makeText(MainActivity.this, "Permission already granted", Toast.LENGTH_SHORT).show();
        }
    }
 
    // This function is called when the user accepts or decline the permission.
    // Request Code is used to check which permission called this function.
    // This request code is provided when the user is prompt for permission.
 
    @Override
    public void onRequestPermissionsResult(int requestCode,
                                        @NonNull String[] permissions,
                                        @NonNull int[] grantResults)
    {
        super.onRequestPermissionsResult(requestCode,
                                        permissions,
                                        grantResults);
 
        if (requestCode == CAMERA_PERMISSION_CODE) {
            if (grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
                Toast.makeText(MainActivity.this, "Camera Permission Granted", Toast.LENGTH_SHORT) .show();
            }
            else {
                Toast.makeText(MainActivity.this, "Camera Permission Denied", Toast.LENGTH_SHORT) .show();
            }
        }
        else if (requestCode == STORAGE_PERMISSION_CODE) {
            if (grantResults.length > 0
                && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
                Toast.makeText(MainActivity.this, "Storage Permission Granted", Toast.LENGTH_SHORT).show();
            } else {
                Toast.makeText(MainActivity.this, "Storage Permission Denied", Toast.LENGTH_SHORT).show();
            }
        }
    }
}

输出：

在启动应用程序时：

第一次单击相机按钮时：

在授予权限时：

再次单击相机按钮时：