我正在尝试创建一个下载内容然后移动它的应用。
当我手动进入应用偏好设置并授予其权限时，该应用有效，但我正在尝试在应用打开时为其授予权限。
到目前为止，这是我的代码
package idkwhatimdoing.com.emojiupdaterroot;
import android.Manifest;
import android.app.DownloadManager;
import android.app.ProgressDialog;
import android.content.Context;
import android.content.pm.PackageManager;
import android.net.Uri;
import android.os.Build;
import android.os.Bundle;
import android.os.Environment;
import android.support.v4.app.ActivityCompat;
import android.support.v4.content.ContextCompat;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.Button;
import android.widget.Spinner;
import java.io.IOException;
public class MainActivity extends AppCompatActivity {
final Spinner emojiSpinner = (Spinner) findViewById(R.id.emojiSpinner);
final String emojiSpinnerText = emojiSpinner.getSelectedItem().toString();
final Button updateEmojiButton = (Button) findViewById(R.id.updateEmojiButton);
// Assume thisActivity is the current activity
private static final int MY_PERMISSIONS_REQUEST_WRITE_EXTERNAL_STORAGE = 0;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
int permissionCheck = ContextCompat.checkSelfPermission(MainActivity.this,
Manifest.permission.WRITE_EXTERNAL_STORAGE);
updateEmojiButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
// Here, thisActivity is the current activity
if (ContextCompat.checkSelfPermission(MainActivity.this,
Manifest.permission.WRITE_EXTERNAL_STORAGE)
!= PackageManager.PERMISSION_GRANTED) {
// Should we show an explanation?
if (ActivityCompat.shouldShowRequestPermissionRationale(MainActivity.this,
Manifest.permission.WRITE_EXTERNAL_STORAGE)) {
// Show an expanation to the user *asynchronously* -- don't block
// this thread waiting for the user's response! After the user
// sees the explanation, try again to request the permission.
} else {
// No explanation needed, we can request the permission.
ActivityCompat.requestPermissions(MainActivity.this,
new String[]{Manifest.permission.WRITE_EXTERNAL_STORAGE},
MY_PERMISSIONS_REQUEST_WRITE_EXTERNAL_STORAGE);
// MY_PERMISSIONS_REQUEST_READ_CONTACTS is an
// app-defined int constant. The callback method gets the
// result of the request.
}
}
}
});
}
@Override
public void onRequestPermissionsResult(int requestCode,
String permissions[], int[] grantResults) {
switch (requestCode) {
case MY_PERMISSIONS_REQUEST_WRITE_EXTERNAL_STORAGE: {
// If request is cancelled, the result arrays are empty.
if (grantResults.length > 0
&& grantResults[0] == PackageManager.PERMISSION_GRANTED) {
ProgressDialog progress = new ProgressDialog(MainActivity.this);
progress.setMessage("Downloading New Emojis");
progress.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
progress.setIndeterminate(true);
progress.show();
try {
Runtime.getRuntime().exec("su");
} catch (IOException e) {
e.printStackTrace();
}
if (emojiSpinnerText.equals("iPhone iOS 9.1")) {
String iosEmojiUrl = "http://idkwhatimdoing/androidapps/iPhone9_1.ttf";
DownloadManager.Request request = new DownloadManager.Request(Uri.parse(iosEmojiUrl));
request.setTitle("Downloading_New_Emojis");
request.setDescription("iPhone iOS 9.1");
// in order for this if to run, you must use the android 3.2 to compile your app
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.HONEYCOMB) {
request.allowScanningByMediaScanner();
request.setNotificationVisibility(DownloadManager.Request.VISIBILITY_VISIBLE_NOTIFY_COMPLETED);
}
request.setDestinationInExternalPublicDir(Environment.DIRECTORY_DOWNLOADS, "NotoColorEmoji.ttf");
progress.setMessage("Updating Emojis");
// get download service and enqueue file
DownloadManager manager = (DownloadManager) getSystemService(Context.DOWNLOAD_SERVICE);
manager.enqueue(request);
} else if (emojiSpinnerText.equals("Android Marshmallow 6.0.1")) {
String iosEmojiUrl = "http://idkwhatimdoing/androidapps/Android6_0_1.ttf";
DownloadManager.Request request = new DownloadManager.Request(Uri.parse(iosEmojiUrl));
request.setTitle("Downloading_New_Emojis");
request.setDescription("Android Marshmallow 6.0.1");
// in order for this if to run, you must use the android 3.2 to compile your app
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.HONEYCOMB) {
request.allowScanningByMediaScanner();
request.setNotificationVisibility(DownloadManager.Request.VISIBILITY_VISIBLE_NOTIFY_COMPLETED);
}
request.setDestinationInExternalPublicDir(Environment.DIRECTORY_DOWNLOADS, "NotoColorEmoji.ttf");
progress.setMessage("Updating Emojis");
// get download service and enqueue file
DownloadManager manager = (DownloadManager) getSystemService(Context.DOWNLOAD_SERVICE);
manager.enqueue(request);
}
} else {
// permission denied, boo! Disable the
// functionality that depends on this permission.
}
return;
}
// other 'case' lines to check for other
// permissions this app might request
}
}
}
我的清单有
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.INTERNET" />
每当我尝试打开应用程序时，它都会强行关闭。
有什么想法吗？
我在Marshmallow 6.0.1上测试了这个
这是我的logcat
02-18 01:27:32.586 20844-20844/idkwhatimdoing.com.emojiupdaterroot E/AndroidRuntime: FATAL EXCEPTION: main
Process: idkwhatimdoing.com.emojiupdaterroot, PID: 20844
java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{idkwhatimdoing.com.emojiupdaterroot/idkwhatimdoing.com.emojiupdaterroot.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'android.view.View android.view.Window.findViewById(int)' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java)
at android.app.ActivityThread.access$900(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java)
at android.os.Handler.dispatchMessage(Handler.java)
at android.os.Looper.loop(Looper.java)
at android.app.ActivityThread.main(ActivityThread.java)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java)
at de.robv.android.xposed.XposedBridge.main(XposedBridge.java:117)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'android.view.View android.view.Window.findViewById(int)' on a null object reference
at android.app.Activity.findViewById(Activity.java)
at idkwhatimdoing.com.emojiupdaterroot.MainActivity.<init>(MainActivity.java:22)
at java.lang.Class.newInstance(Native Method)
at android.app.Instrumentation.newActivity(Instrumentation.java)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java)
at android.app.ActivityThread.access$900(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java)
at android.os.Handler.dispatchMessage(Handler.java)
at android.os.Looper.loop(Looper.java)
at android.app.ActivityThread.main(ActivityThread.java)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java)
at de.robv.android.xposed.XposedBridge.main(XposedBridge.java:117)
答案 0 :(得分：1)
方法checkSelfPermission（String）已添加到API 23.在API 23下面它没有用，因为总是授予权限。在处理权限之前检查API版本
int permissionCheck = 0;
if (Build.VERSION.SDK_INT < Build.VERSION_CODES.M) {
permissionCheck = ContextCompat.checkSelfPermission(MainActivity.this,
Manifest.permission.WRITE_EXTERNAL_STORAGE);
}
答案 1 :(得分：0)
if (Build.VERSION.SDK_INT >= 23) {
if (checkSelfPermission(android.Manifest.permission.WRITE_EXTERNAL_STORAGE)
== PackageManager.PERMISSION_GRANTED) {
Log.e("testing", "Permission is granted");
} else {
ActivityCompat.requestPermissions(this, new String[]{Manifest.permission.WRITE_EXTERNAL_STORAGE}, 1);
Log.e("testing", "Permission is revoked");
}
} else { //permission is automatically granted on sdk<23 upon installation
Log.e("testing", "Permission is already granted");
Grant permission in this way hope it may be help you
答案 2 :(得分：0)
试试这个..
在清单文件中的MainActivity中添加主题，如下所示 机器人：主题=＆＃34; @风格/ Theme.AppCompat.Light.NoActionBar＆＃34;
答案 3 :(得分：0)
我不知道您是否找到了，但问题不是权限，而是代码。
final Spinner emojiSpinner = (Spinner) findViewById(R.id.emojiSpinner);
final String emojiSpinnerText = emojiSpinner.getSelectedItem().toString();
final Button updateEmojiButton = (Button) findViewById(R.id.updateEmojiButton);
您应该在onCreate（）方法中指定值。 Logcat清楚地说明了
引起：java.lang.NullPointerException：尝试调用虚方法＆＃39; android.view.View android.view.Window.findViewById（int）＆＃39;在空对象引用上
您应该采取以下方式：
final Spinner emojiSpinner;
final String emojiSpinnerText;
final Button updateEmojiButton;
和onCreate（）
emojiSpinner = (Spinner) findViewById(R.id.emojiSpinner);
emojiSpinnerText = emojiSpinner.getSelectedItem().toString();
updateEmojiButton = (Button) findViewById(R.id.updateEmojiButton);
答案 4 :(得分：0)
我添加了以下内容：
@Override
public void onRequestPermissionsResult(int requestCode, String[] permissions, int[] grantResults){
//What you want to do when permissions are met
}