在Android 7上写入外部存储

Question

我想在Android应用程序中写入外部存储，但我似乎没有获得正确的权限。该应用程序在Android 7上运行，因此我请求如下运行时权限：

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
permission = ActivityCompat.checkSelfPermission(this, Manifest.permission.WRITE_EXTERNAL_STORAGE);

if (permission != PackageManager.PERMISSION_GRANTED) {
    // We don't have permission so prompt the user
    int ACCESS_EXTERNAL_STORAGE_STATE = 1;
    ActivityCompat.requestPermissions(this,
            new String[]{Manifest.permission.WRITE_EXTERNAL_STORAGE},
            ACCESS_EXTERNAL_STORAGE_STATE);
}

permission = ActivityCompat.checkSelfPermission(this, Manifest.permission.READ_EXTERNAL_STORAGE);

if (permission != PackageManager.PERMISSION_GRANTED) {
    // We don't have permission so prompt the user
    int ACCESS_EXTERNAL_STORAGE_STATE = 1;
    ActivityCompat.requestPermissions(this,
            new String[]{Manifest.permission.READ_EXTERNAL_STORAGE},
            ACCESS_EXTERNAL_STORAGE_STATE);
}
...
    @Override
    public void onRequestPermissionsResult(int requestCode, String[] permissions, int[] grantResults) {
        super.onRequestPermissionsResult(requestCode, permissions, grantResults);
        switch (requestCode)
        {
            case 1: {
                if (grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED)
                {
                    //reload my activity with permission granted or use the features what required the permission
                } else
                {
                    Toast.makeText(this, "The app was not allowed to write to your storage. Hence, it cannot function properly. Please consider granting it this permission", Toast.LENGTH_LONG).show();
                }
            }
        }
    }

我的一个观察是，onRequest estPermissionsResult似乎返回未授予权限，但在启动应用程序时也从未提示我允许写入外部存储。

    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
    <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
    <application>

要写入存储的代码如下：

public static void appendByteBuffer(byte[] data)
{
    String filename = Environment.getExternalStorageDirectory().getAbsolutePath()+"/test.raw";
    //filename value is "/storage/emulated/0/test.raw"
    File rawAudioFile = new File(filename);
    if (!rawAudioFile.exists())
    {
        try
        {
            rawAudioFile.createNewFile();
        }
        catch (IOException e)
        {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
    try (FileOutputStream output = new FileOutputStream(filename, true)) {
        output.write(data);
    } catch (IOException e) {}
}

03-16 14:50:49.988 19145-19306/? 带系统。错误：java。io。IOException：权限被拒绝03-16 14:50:49.988 19145-19306/？带系统。错误：
在java。io。UnixFileSystem。createFileExclusively0（本机方法）03-16 14:50:49.988 19145-19306/？带系统。错误：在java。io。UnixFileSystem。CreateFileExclusive（UnixFileSystem.java:280）03-16 14:50:49.989 19145-19306/？带系统。错误：在java。io。文件createNewFile（File.java:948）03-16 14:50:49.989 19145-19306/？带系统。错误：位于com。米特。学习附件。附录Buffer（AppUtils.java:76）03-16 14:50:49.989 19145-19306/？带系统。错误：位于

Answer 1

使用ContextCompat而不是ActivityCompat来检查selfpermission：

替换：

permission = ActivityCompat.checkSelfPermission(this, Manifest.permission.WRITE_EXTERNAL_STORAGE);
permission = ActivityCompat.checkSelfPermission(this, Manifest.permission.READ_EXTERNAL_STORAGE);

与：

permission = ContextCompat.checkSelfPermission(this, Manifest.permission.WRITE_EXTERNAL_STORAGE);
permission = ContextCompat.checkSelfPermission(this, Manifest.permission.READ_EXTERNAL_STORAGE);

然后，添加onRequestPermissionsResult方法来处理允许、拒绝选择。希望这有帮助。

@Override
public void onRequestPermissionsResult(int requestCode, String[] permissions, int[] grantResults) {
        switch (requestCode) {
            case ACCESS_EXTERNAL_STORAGE_STATE: {
                // If request is cancelled, the result arrays are empty.
                if (grantResults.length > 0
                        && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
                   // Write to the storage (ex: call appendByteBuffer(byte[] data) here)

                } else {
                    Toast.makeText(getApplicationContext(), "Please grant permission.", Toast.LENGTH_LONG).show();
                }
                break;
            }
}