我正在尝试制作一个应用程序，它可以下载某些东西并将其移动。
当我手动进入应用程序偏好设置并授予权限时，该应用程序可以正常工作，但是我正在尝试在应用程序打开时授予权限。
以下是我目前的代码：
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" />
每当我尝试打开这个应用时，它就会强制关闭。
你有什么想法吗？
我正在Marhsmallow 6.0.1上进行测试。
以下是我的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)
ContextCompat是因为它会为你进行版本检查，并在旧版本上返回PackageManager.PERMISSION_GRANTED。 - ianhanniballake