java - 我的应用程序在启动时崩溃

Question

我的应用程序在启动时崩溃，但没有显示任何错误。
我找不到原因。我尝试了很多解决方案，但都是徒劳

这里是MainActivity.java

package com.example.android.mycourses;

import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.widget.CheckBox;
import android.widget.CompoundButton;
import android.widget.ListView;
import android.widget.TextView;

import com.google.firebase.database.ChildEventListener;
import com.google.firebase.database.DataSnapshot;
import com.google.firebase.database.DatabaseError;
import com.google.firebase.database.DatabaseReference;
import com.google.firebase.database.FirebaseDatabase;

import java.util.ArrayList;

public class MainActivity extends AppCompatActivity {

    private FirebaseDatabase mfirebasedatabase; //to access the database
    private DatabaseReference mDatabase; //class references a specific part of the database
    private ChildEventListener mchildEventListener; //to read from the database


    TextView courseTV;
    CheckBox checkbox;
    CourseAdapter adapter;


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

        mfirebasedatabase=FirebaseDatabase.getInstance();//to instantiate the database(this is the access point to the database)
        mDatabase=mfirebasedatabase.getReference().child("courses");

        courseTV = (TextView) findViewById(R.id.messageTextView);
        populateUsersList();

        checkbox = ( CheckBox ) findViewById( R.id.checkbox );
        checkbox.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener()
        {
            public void onCheckedChanged(CompoundButton buttonView, boolean isChecked)
            {
                if ( isChecked )
                {
                    // save in database
                    Course cc=new Course(courseTV.getText().toString());
                    mDatabase.push().setValue(cc);
                }
                else if(!isChecked){
                    //remove from database
                }
            }
        });
        mchildEventListener =new ChildEventListener(){
            @Override
        public void onChildAdded(DataSnapshot dataSnapshot, String s) {
            Course c=dataSnapshot.getValue(Course.class);
            adapter.add(c);
        }

            @Override
            public void onChildChanged(DataSnapshot dataSnapshot, String s) {

            }

            @Override
            public void onChildRemoved(DataSnapshot dataSnapshot) {

            }

            @Override
            public void onChildMoved(DataSnapshot dataSnapshot, String s) {

            }

            @Override
            public void onCancelled(DatabaseError databaseError) {

            }
        };
        mDatabase.addChildEventListener(mchildEventListener);


    }
    private void populateUsersList() {
        // Construct the data source
        ArrayList<Course> arrayOfUsers = Course.getCourses();
        // Create the adapter to convert the array to views
        CourseAdapter adapter = new CourseAdapter(this, arrayOfUsers);
        // Attach the adapter to a ListView
        ListView listView = (ListView) findViewById(R.id.listView);
        listView.setAdapter(adapter);
    }
}

这里是activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context="com.example.android.mycourses.MainActivity">

 <ListView
     android:layout_width="wrap_content"
     android:layout_height="wrap_content"
     android:id="@+id/listView"></ListView>


</RelativeLayout>

这里是 item_message.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_marginLeft="@dimen/activity_horizontal_margin"
    android:layout_marginStart="@dimen/activity_horizontal_margin"
    android:orientation="vertical">

    <TextView
        android:id="@+id/messageTextView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_weight="0"
        android:textAppearance="?android:attr/textAppearanceLarge"
        tools:text="course" />
    <CheckBox
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:id="@+id/checkbox"
        android:layout_alignRight="@+id/messageTextView"/>

</RelativeLayout>

这是日志显示给我的内容

   02-16 16:57:52.515 9095-9095/? I/art: Late-enabling -Xcheck:jni
    02-16 16:57:52.647 9095-9095/com.example.android.mycourses W/System: ClassLoader referenced unknown path: /data/app/com.example.android.mycourses-1/lib/arm64
    02-16 16:57:52.686 9095-9095/com.example.android.mycourses I/FA: App measurement is starting up, version: 10084
    02-16 16:57:52.686 9095-9095/com.example.android.mycourses I/FA: To enable debug logging run: adb shell setprop log.tag.FA VERBOSE
    02-16 16:57:52.703 9095-9095/com.example.android.mycourses I/FA: To enable faster debug mode event logging run:
                                                                       adb shell setprop debug.firebase.analytics.app com.example.android.mycourses
    02-16 16:57:52.712 9095-9095/com.example.android.mycourses I/HwCust: Constructor found for class android.app.HwCustAlarmManagerImpl
    02-16 16:57:52.722 9095-9095/com.example.android.mycourses I/FirebaseInitProvider: FirebaseApp initialization successful
    02-16 16:57:52.775 9095-9095/com.example.android.mycourses W/art: Before Android 4.1, method android.graphics.PorterDuffColorFilter android.support.graphics.drawable.VectorDrawableCompat.updateTintFilter(android.graphics.PorterDuffColorFilter, android.content.res.ColorStateList, android.graphics.PorterDuff$Mode) would have incorrectly overridden the package-private method in android.graphics.drawable.Drawable
    02-16 16:57:52.894 9095-9095/com.example.android.mycourses I/DynamiteModule: Considering local module com.google.android.gms.firebase_database:4 and remote module com.google.android.gms.firebase_database:5
    02-16 16:57:52.894 9095-9095/com.example.android.mycourses I/DynamiteModule: Selected remote version of com.google.android.gms.firebase_database, version >= 5
    02-16 16:57:52.911 9095-9095/com.example.android.mycourses W/System: ClassLoader referenced unknown path: /data/user/0/com.google.android.gms/app_chimera/m/00000007/n/arm64-v8a
    02-16 16:57:52.967 9095-9144/com.example.android.mycourses I/System: core_booster, getBoosterConfig = false
    02-16 16:57:52.989 9095-9095/com.example.android.mycourses I/Process: Sending signal. PID: 9095 SIG: 9

Answer 1

尝试清理您的构建:(设置 -> 应用程序 -> MyApp -> 内存 -> 清除数据)已知可以修复类加载器问题。

否则您的 xml 布局可能有问题。