我有一个Android应用。该应用程序有十个活动，其中第一个活动是“启动画面”，并且运行了介绍活动，进入主活动后出现错误，该应用程序关闭且未进入主活动，我得到的错误是：
E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.myapplication, PID: 28709
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.myapplication/com.example.myapplication.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.view.View.setAlpha(float)' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2665)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2726)
at android.app.ActivityThread.-wrap12(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1477)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:154)
at android.app.ActivityThread.main(ActivityThread.java:6119)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.view.View.setAlpha(float)' on a null object reference
at com.github.hujiaweibujidao.wava.BaseViewAnimator.reset(BaseViewAnimator.java:78)
at com.github.hujiaweibujidao.wava.BaseViewAnimator.start(BaseViewAnimator.java:55)
at com.github.hujiaweibujidao.wava.YoYo$Builder.start(YoYo.java:128)
at com.github.hujiaweibujidao.wava.YoYo$Builder.playOn(YoYo.java:115)
at com.example.myapplication.MainActivity.onCreate(MainActivity.java:104)
at android.app.Activity.performCreate(Activity.java:6679)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1118)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2618)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2726)
at android.app.ActivityThread.-wrap12(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1477)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:154)
at android.app.ActivityThread.main(ActivityThread.java:6119)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776)
我的xml代码：
<?xml version="1.0" encoding="utf-8"?>
<com.mxn.soul.flowingdrawer_core.FlowingDrawer
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:night="http://schemas.android.com/tools"
android:id="@+id/drawerlayout"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:clipChildren="false"
android:clipToPadding="false"
app:edPosition="2"
app:edMenuSize="260dp"
app:edMenuBackground="#dddddd">
<LinearLayout
android:id="@+id/lin_main"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
>
<androidx.appcompat.widget.Toolbar
android:layout_width="match_parent"
android:layout_height="?attr/actionBarSize"
android:background="@color/nephritis"
android:id="@+id/toolbar"
>
<androidx.constraintlayout.widget.ConstraintLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="horizontal"
android:gravity="end">
<androidx.appcompat.widget.AppCompatImageView
android:id="@+id/img_night"
android:layout_width="35dp"
android:layout_height="35dp"
android:layout_margin="8dp"
android:background="@drawable/moon_icon"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent"
android:onClick="set_night"/>
<TextView
android:id="@+id/txt_text"
android:layout_width="0dp"
android:layout_height="match_parent"
android:layout_margin="4dp"
android:layout_marginStart="8dp"
android:layout_marginLeft="8dp"
android:layout_marginEnd="8dp"
android:layout_marginRight="8dp"
android:fontFamily="@font/medium"
android:gravity="center_vertical"
android:lineSpacingExtra="10dp"
android:text="@string/martaei"
android:textColor="@color/White"
android:textSize="26sp"
app:layout_constraintEnd_toStartOf="@+id/img_icon"
app:layout_constraintStart_toEndOf="@+id/img_night"
night:layout_editor_absoluteY="4dp"
night:night_textColor="#180101" />
<androidx.appcompat.widget.AppCompatImageView
android:id="@+id/img_icon"
android:layout_width="50dp"
android:layout_height="50dp"
android:layout_centerInParent="true"
android:layout_margin="4dp"
android:src="@drawable/menu"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintTop_toTopOf="parent" />
</androidx.constraintlayout.widget.ConstraintLayout>
</androidx.appcompat.widget.Toolbar>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="0dp"
android:layout_weight="3"
android:gravity="center">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="horizontal"
android:weightSum="2"
android:gravity="center">
<androidx.appcompat.widget.AppCompatImageView
android:id="@+id/img_main"
android:layout_width="0dp"
android:layout_weight="1.5"
android:layout_height="match_parent"
android:background="@drawable/ic_profile123456"
android:layout_gravity="center"
android:layout_margin="12sp"/>
</LinearLayout>
</LinearLayout>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="0dp"
android:layout_weight="4"
android:orientation="vertical">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:gravity="center"
android:orientation="horizontal"
android:weightSum="2"
android:layout_marginTop="36dp">
<Button
android:id="@+id/btn_fehrest"
android:layout_width="0dp"
android:layout_weight="1"
android:layout_height="80dp"
android:text="@string/listmozo"
android:textSize="24sp"
android:textColor="@color/White"
android:fontFamily="@font/medium"
android:onClick="fehrest_intent"
android:background="@drawable/back_btn1"
android:layout_gravity="center"
android:paddingEnd="12dp"/>
</LinearLayout>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:gravity="center"
android:orientation="horizontal"
android:weightSum="2">
<Button
android:id="@+id/btn_last_story"
android:layout_width="0dp"
android:layout_weight="1"
android:layout_height="80dp"
android:text="آخرین داستان"
android:onClick="text_intent"
android:textSize="24sp"
android:textColor="@color/White"
android:fontFamily="@font/medium"
android:background="@drawable/back_btn3"
android:layout_gravity="center"
android:paddingEnd="12dp"/>
</LinearLayout>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:gravity="center"
android:orientation="horizontal"
android:weightSum="2">
<Button
android:id="@+id/btn_fav"
android:layout_width="0dp"
android:layout_weight="1"
android:layout_height="80dp"
android:text="@string/list_of_favorites"
android:onClick="fav_intent"
android:textSize="24dp"
android:textColor="@color/White"
android:fontFamily="@font/medium"
android:background="@drawable/back_btn2"
android:layout_gravity="center"
android:paddingRight="12dp"/>
</LinearLayout>
</LinearLayout>
<RelativeLayout
android:layout_width="match_parent"
android:layout_height="0dp"
android:layout_weight="1"
android:layout_margin="8dp">
<com.akshay.library.CurveBottomBar
android:layout_width="match_parent"
android:layout_height="60dp"
android:layout_alignParentBottom="true"
app:bottomBarColor="#FFB601"
app:curveRadius="53dp"
app:itemIconTint="@color/White"
android:id="@+id/cbb"/>
</RelativeLayout>
</LinearLayout>
<com.mxn.soul.flowingdrawer_core.FlowingMenuLayout
android:id="@+id/menulayout"
android:layout_width="match_parent"
android:layout_height="match_parent"
>
<androidx.appcompat.widget.LinearLayoutCompat
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
android:gravity="end"
android:background="@color/White">
<androidx.appcompat.widget.AppCompatImageView
android:id="@+id/imgtest"
android:layout_width="wrap_content"
android:layout_height="200dp"
android:scaleType="centerCrop"
android:background="@drawable/back_nav"/>
<androidx.appcompat.widget.LinearLayoutCompat
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="horizontal"
android:gravity="end|center_vertical"
android:layout_margin="8dp">
<TextView
android:id="@+id/txt"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="@string/ghhgkjjjhjl"
android:layout_margin="8dp"
android:onClick="fehrest_intent"/>
<androidx.appcompat.widget.AppCompatImageView
android:layout_width="20dp"
android:layout_height="20dp"
android:background="@drawable/content_copy2"/>
</androidx.appcompat.widget.LinearLayoutCompat>
<androidx.appcompat.widget.LinearLayoutCompat
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="horizontal"
android:gravity="end|center_vertical"
android:layout_margin="8dp">
<TextView
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="@string/hghjk"
android:layout_margin="8dp"
android:onClick="fav_intent"/>
<androidx.appcompat.widget.AppCompatImageView
android:layout_width="20dp"
android:layout_height="20dp"
android:background="@drawable/heart_icon"
android:onClick="fav_intent"/>
</androidx.appcompat.widget.LinearLayoutCompat>
<androidx.appcompat.widget.LinearLayoutCompat
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="horizontal"
android:gravity="end|center_vertical"
android:layout_margin="8dp">
<androidx.appcompat.widget.AppCompatImageView
android:layout_width="20dp"
android:layout_height="20dp"
android:background="@drawable/settings2"/>
</androidx.appcompat.widget.LinearLayoutCompat>
<androidx.appcompat.widget.LinearLayoutCompat
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="horizontal"
android:gravity="end|center_vertical"
android:layout_margin="8dp">
</androidx.appcompat.widget.LinearLayoutCompat>
<View
android:layout_width="match_parent"
android:layout_height="1dp"
android:background="@color/gray"
android:layout_margin="8dp"/>
<androidx.appcompat.widget.LinearLayoutCompat
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="horizontal"
android:gravity="end|center_vertical"
android:layout_margin="8dp">
</androidx.appcompat.widget.LinearLayoutCompat>
<androidx.appcompat.widget.LinearLayoutCompat
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="horizontal"
android:gravity="end|center_vertical"
android:layout_margin="8dp">
<TextView
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="@string/jkhjlkjkl"
android:layout_margin="8dp"/>
<androidx.appcompat.widget.AppCompatImageView
android:layout_width="20dp"
android:layout_height="20dp"
android:background="@drawable/content_copy2"/>
</androidx.appcompat.widget.LinearLayoutCompat>
<androidx.appcompat.widget.LinearLayoutCompat
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="horizontal"
android:gravity="end|center_vertical"
android:layout_margin="8dp">
<TextView
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="@string/klkl"
android:layout_margin="8dp"
android:onClick="finish"/>
<ImageView
android:layout_width="20dp"
android:layout_height="20dp"
android:background="@drawable/exit_to_app"/>
</androidx.appcompat.widget.LinearLayoutCompat>
</androidx.appcompat.widget.LinearLayoutCompat>
</com.mxn.soul.flowingdrawer_core.FlowingMenuLayout>
</com.mxn.soul.flowingdrawer_core.FlowingDrawer>
我的Java代码：
package com.example.myapplication;
public class MainActivity extends AppCompatActivity {
private CurveBottomBar cbb;
FlowingDrawer mDrawer;
ImageView img_icon,imgtest,img_music,img_night,img_main,img_setting;
TextView txt;
String patch;
boolean read=false,music=true,night_mode;
Button btn_fehrest,btn_last_story,btn_fav;
SharedPreferences sharedP;
LinearLayout lin_main;
Toast exit;
boolean show_intropage;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
cbb = findViewById(R.id.cbb);
mDrawer = findViewById(R.id.drawerlayout);
imgtest = findViewById(R.id.imgtest);
txt = findViewById(R.id.txt);
btn_fehrest = findViewById(R.id.btn_fehrest);
img_music = findViewById(R.id.img_music);
lin_main = findViewById(R.id.lin_main);
img_night = findViewById(R.id.img_night);
img_main = findViewById(R.id.img_main);
btn_fav = findViewById(R.id.btn_fav);
img_setting = findViewById(R.id.img_setting);
cbb.inflateMenu(R.menu.menu_scrolling);
sharedP = getSharedPreferences(Items.SETTINGS, Context.MODE_PRIVATE);
show_intropage = sharedP.getBoolean(Items.INTROPAGE,true);
cbb.setOnNavigationItemSelectedListener(new BottomNavigationView.OnNavigationItemSelectedListener() {
@Override
public boolean onNavigationItemSelected(@NonNull MenuItem menuItem) {
switch (menuItem.getItemId()){
case R.id.img_setting:
// kary ke mikhaym anjam bedim
break;
case R.id.img_music:
//
break;
}
return true;
}
});
YoYo.with(Techniques.ZoomInDown).duration(1000).playOn(btn_fehrest);
YoYo.with(Techniques.ZoomInDown).duration(1000).playOn(btn_last_story);
YoYo.with(Techniques.ZoomInDown).duration(1000).playOn(btn_fav);
YoYo.with(Techniques.ZoomInDown).duration(1000).playOn(img_music);
YoYo.with(Techniques.ZoomInDown).duration(1000).playOn(img_setting);
get_night();
permission();
//createFile();
if (show_intropage){
taptarget();
}
img_icon.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
mDrawer.openMenu(true);
}
});
mDrawer.setTouchMode(ElasticDrawer.TOUCH_MODE_BEZEL);
mDrawer.setBackgroundColor(Color.WHITE);
mDrawer.setOnDrawerStateChangeListener(new ElasticDrawer.OnDrawerStateChangeListener() {
@Override
public void onDrawerStateChange(int oldState, int newState) {
if (newState == ElasticDrawer.STATE_CLOSED) {
Log.i("MainActivity", "Drawer STATE_CLOSED");
}
}
@Override
public void onDrawerSlide(float openRatio, int offsetPixels) {
Log.i("MainActivity", "openRatio=" + openRatio + " ,offsetPixels=" + offsetPixels);
}
});
}
public void createFile(){
try {
patch = Environment.getExternalStorageDirectory().getAbsolutePath() + "/Mbook/";
File mfile = new File(patch);
if (!mfile.exists()) {
mfile.mkdir();
mfile.createNewFile();
CopyDB(getBaseContext().getAssets().open("Mbook.db"), new FileOutputStream(patch+"/Mbook.db"));
//Toast.makeText(this, patch+"", Toast.LENGTH_LONG).show();
}
}catch (FileNotFoundException e){
e.printStackTrace();
}catch (IOException e){
e.printStackTrace();
}
}
public void CopyDB (InputStream inputStream, OutputStream outputStream) throws IOException {
byte[] buffer = new byte[1024];
int file_length;
while ((file_length = inputStream.read(buffer))>0){
outputStream.write(buffer,0,file_length);
}
inputStream.close();
outputStream.close();
}
public void fehrest_intent(View view) {
mDrawer.closeMenu(true);
YoYo.with(Techniques.Pulse).duration(800).playOn(btn_fehrest);
new Handler().postDelayed(new Runnable() {
@Override
public void run() {
Intent intent = new Intent(getBaseContext(), Fehrest.class);
intent.putExtra("button","fehrest");
startActivity(intent);
}
},1500);
}
private void permission(){
Dexter.withActivity(MainActivity.this)
.withPermission(Manifest.permission.WRITE_EXTERNAL_STORAGE)
.withListener(new PermissionListener() {
@Override
public void onPermissionGranted(PermissionGrantedResponse response) {
createFile();
}
@Override
public void onPermissionDenied(PermissionDeniedResponse response) {
if (response !=null && response.isPermanentlyDenied()){
@Override
public void onClick(DialogInterface dialogInterface, int i) {
Intent intent = new Intent(Settings.ACTION_APPLICATION_DETAILS_SETTINGS);
intent.setData(Uri.fromParts("package",getPackageName(),null));
startActivity(intent);
}
});
}
@Override
public void onPermissionRationaleShouldBeShown(PermissionRequest permission, final PermissionToken token) {
alert();
}
}).check();
}
Hoshdar.create().show();
}
public void fav_intent(View view) {
YoYo.with(Techniques.Pulse).duration(600).playOn(btn_fav);
mDrawer.closeMenu(true);
new Handler().postDelayed(new Runnable() {
@Override
public void run() {
Intent intent = new Intent(getBaseContext(), Fehrest.class);
intent.putExtra("button","fav");
intent.putExtra("activity","main");
startActivity(intent);
}
},1500);
}
public void setting_intent(MenuItem item) {
mDrawer.closeMenu(true);
YoYo.with(Techniques.Pulse).duration(600).playOn(img_setting);
new Handler().postDelayed(new Runnable() {
@Override
public void run() {
startActivity(new Intent(MainActivity.this,Setting.class));
}
},1500);
}
public void set_music(MenuItem item) {
YoYo.with(Techniques.Pulse).duration(600).playOn(img_music);
if (music){
stopService(new Intent(MainActivity.this,PlayMusic.class));
img_music.setBackgroundResource(R.drawable.music_off_icon);
music=false;
sharedP.edit().putBoolean(Items.MUSIC, false).apply();
}else {
startService(new Intent(MainActivity.this,PlayMusic.class));
img_music.setBackgroundResource(R.drawable.music_on_icon);
music=true;
sharedP.edit().putBoolean(Items.MUSIC, true).apply();
}
}
上面的代码是用Android Studio编写的。我使用软件的虚拟设备。我希望你能帮助我
请遵循以下选项。希望您的问题得到解决。
1）您的清单必须像此活动名称一样更改必须与“ .YourActivityname”一样指定
2）清理并重建该项目，希望它能正常工作。