Android 请求运行时权限

写文件到sd卡中，会报权限问题，需要动态申请申请运行时权限

1. MainActivity.java

public class MainActivity extends Activity {
    private final static String TAG = "MainActivity11";private final static int EXTERNAL_STORAGE_REQUEST_CODE = 1;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        if (checkSelfPermission(Manifest.permission.WRITE_EXTERNAL_STORAGE) != PackageManager.PERMISSION_GRANTED) {
            requestPermissions(new String[] { Manifest.permission.WRITE_EXTERNAL_STORAGE }, EXTERNAL_STORAGE_REQUEST_CODE);
            } else {
            // 已经授权了，第二次就可以正常写卡操作了
        }
    }

    @Override
    public void onRequestPermissionsResult(int requestCode, String[] permissions, int[] grantResults) {
        super.onRequestPermissionsResult(requestCode, permissions, grantResults);
        switch (requestCode) {
        case EXTERNAL_STORAGE_REQUEST_CODE:
　　　　　　 // 用户点击权限对话框，确认后，会回调到这里,然后进行写卡操作
            break;
        }
    }
}

2.AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.android.mdm"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-sdk
        android:minSdkVersion="25"
        android:targetSdkVersion="25" />

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

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

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

</manifest>