我编写了一个 Android 应用程序，使用 DownloadManager 将示例 PDF 文件下载到下载目录。这是代码:
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_vertretungsplan);
Button dlbutton = (Button) findViewById(R.id.buttondownload);
final Context c = this;
dlbutton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
DownloadManager.Request request = new DownloadManager.Request(Uri.parse(myurl));
request.setTitle("Vertretungsplan");
request.setDescription("wird heruntergeladen");
request.allowScanningByMediaScanner();
request.setNotificationVisibility(DownloadManager.Request.VISIBILITY_VISIBLE_NOTIFY_COMPLETED);
String filename = URLUtil.guessFileName(myurl, null, MimeTypeMap.getFileExtensionFromUrl(myurl));
request.setDestinationInExternalPublicDir(Environment.DIRECTORY_DOWNLOADS, filename);
DownloadManager manager = (DownloadManager) c.getSystemService(Context.DOWNLOAD_SERVICE);
manager.enqueue(request);
}
});
}
现在，我尝试在我的 Xperia Z3 Android 6.0 上从 Android Studio 调试运行它。 当我点击下载按钮时，出现了这个错误:
E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.markwitt.schul_app, PID: 29297
java.lang.SecurityException: No permission to write to /storage/emulated/0/Download/hrpsampletable.pdf: Neither user 10047 nor current process has android.permission.WRITE_EXTERNAL_STORAGE.
at android.os.Parcel.readException(Parcel.java:1627)
at android.database.DatabaseUtils.readExceptionFromParcel(DatabaseUtils.java:183)
at android.database.DatabaseUtils.readExceptionFromParcel(DatabaseUtils.java:135)
at android.content.ContentProviderProxy.insert(ContentProviderNative.java:476)
at android.content.ContentResolver.insert(ContentResolver.java:1240)
at android.app.DownloadManager.enqueue(DownloadManager.java:946)
at com.example.markwitt.schul_app.Vertretungsplan$1.onClick(Vertretungsplan.java:59)
at android.view.View.performClick(View.java:5280)
at android.view.View$PerformClick.run(View.java:21239)
at android.os.Handler.handleCallback(Handler.java:739)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:224)
at android.app.ActivityThread.main(ActivityThread.java:5526)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
与目标虚拟机断开连接，地址:'localhost:8600'，传输:'socket'
(在第三行)它显示它对外部存储没有写权限。
但我的 AndroidManifest 设置正确:
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.markwitt.schul_app">
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.INTERNET" />
<application
android:launchMode="singleTop"
android:allowBackup="true"
android:icon="@mipmap/ic_launcher"
android:label="@string/app_name"
android:supportsRtl="true"
android:theme="@style/AppTheme">
<activity android:name=".Stundenplan">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity android:name=".Vertretungsplan"></activity>
</application>
我需要做什么？
最佳答案
您收到此错误是因为您的应用在 Android 6.0(API 级别 23)中运行。从 API 级别 >= 23 开始，您将需要在运行时检查权限。您的代码在 23 级以下就可以了。所以请先检查您的用户是否已授予使用存储的权限:
if (checkSelfPermission(android.Manifest.permission.WRITE_EXTERNAL_STORAGE) == PackageManager.PERMISSION_GRANTED) {
Log.e("Permission error","You have permission");
return true;
}
如果没有则提示请求:
ActivityCompat.requestPermissions(this, new String[]{Manifest.permission.WRITE_EXTERNAL_STORAGE}, REQUEST_CODE);
总的来说是这样的:
public boolean haveStoragePermission() {
if (Build.VERSION.SDK_INT >= 23) {
if (checkSelfPermission(android.Manifest.permission.WRITE_EXTERNAL_STORAGE)
== PackageManager.PERMISSION_GRANTED) {
Log.e("Permission error","You have permission");
return true;
} else {
Log.e("Permission error","You have asked for permission");
ActivityCompat.requestPermissions(this, new String[]{Manifest.permission.WRITE_EXTERNAL_STORAGE}, 1);
return false;
}
}
else { //you dont need to worry about these stuff below api level 23
Log.e("Permission error","You already have the permission");
return true;
}
}
最后一件事 :) 通过回调接收结果:
@Override
public void onRequestPermissionsResult(int requestCode, String[] permissions, int[] grantResults) {
super.onRequestPermissionsResult(requestCode, permissions, grantResults);
if(grantResults[0]== PackageManager.PERMISSION_GRANTED){
//you have the permission now.
DownloadManager.Request request = new DownloadManager.Request(Uri.parse(myurl));
request.setTitle("Vertretungsplan");
request.setDescription("wird heruntergeladen");
request.allowScanningByMediaScanner();
request.setNotificationVisibility(DownloadManager.Request.VISIBILITY_VISIBLE_NOTIFY_COMPLETED);
String filename = URLUtil.guessFileName(myurl, null, MimeTypeMap.getFileExtensionFromUrl(myurl));
request.setDestinationInExternalPublicDir(Environment.DIRECTORY_DOWNLOADS, filename);
DownloadManager manager = (DownloadManager) c.getSystemService(Context.DOWNLOAD_SERVICE);
manager.enqueue(request);
}
}
或者，您可以只使用我的自定义类 PermissionCheck 来非常轻松地处理所有这些实现。这是类(class):
import android.Manifest;
import android.app.Activity;
import android.content.Context;
import android.content.pm.PackageManager;
import android.support.v4.app.ActivityCompat;
/**
* Created by Tushar on 6/30/2017.
*/
public class PermissionCheck{
public static boolean readAndWriteExternalStorage(Context context){
if(ActivityCompat.checkSelfPermission(context, Manifest.permission.READ_EXTERNAL_STORAGE) != PackageManager.PERMISSION_GRANTED || ActivityCompat.checkSelfPermission(context, Manifest.permission.WRITE_EXTERNAL_STORAGE) != PackageManager.PERMISSION_GRANTED){
ActivityCompat.requestPermissions((Activity) context, new String[]{Manifest.permission.READ_EXTERNAL_STORAGE, Manifest.permission.READ_EXTERNAL_STORAGE}, 1);
return false;
}else{
return true;
}
}
public static boolean audioRecord(Context context){
if(ActivityCompat.checkSelfPermission(context, Manifest.permission.RECORD_AUDIO) != PackageManager.PERMISSION_GRANTED ){
ActivityCompat.requestPermissions((Activity) context, new String[]{Manifest.permission.RECORD_AUDIO}, 2);
return false;
}else{
return true;
}
}
public static boolean readAndWriteContacts(Context context){
if(ActivityCompat.checkSelfPermission(context, Manifest.permission.READ_CONTACTS) != PackageManager.PERMISSION_GRANTED || ActivityCompat.checkSelfPermission(context, Manifest.permission.WRITE_CONTACTS) != PackageManager.PERMISSION_GRANTED){
ActivityCompat.requestPermissions((Activity) context, new String[]{Manifest.permission.READ_CONTACTS, Manifest.permission.WRITE_CONTACTS}, 3);
return false;
}else{
return true;
}
}
public static boolean vibrate(Context context){
if(ActivityCompat.checkSelfPermission(context, Manifest.permission.VIBRATE) != PackageManager.PERMISSION_GRANTED){
ActivityCompat.requestPermissions((Activity) context, new String[]{Manifest.permission.VIBRATE}, 4);
return false;
}else{
return true;
}
}
public static boolean sendSms(Context context){
if(ActivityCompat.checkSelfPermission(context, Manifest.permission.SEND_SMS) != PackageManager.PERMISSION_GRANTED){
ActivityCompat.requestPermissions((Activity) context, new String[]{Manifest.permission.SEND_SMS}, 5);
return false;
}else{
return true;
}
}
//Just like this you can implement rest of the permissions.
}
用法:
if(PermissionCheck.readAndWriteExternalStorage(context)){
//Your read write code.
}
if(PermissionCheck.sendSms(context)){
//Your sms sending code.
}
**请注意，这些方法调用将自动请求权限，并且您的 onRequestPermissionsResult 将被触发。 :)
关于android - 下载管理器 Android 权限错误 : write external Storage，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/40514335/