最近开始研究AndROId Studio发现一个listView的坑，就是constraint布局是不能直接显示listView的，需要借助水平或垂直布局来显示，否则系统无法显示会直接闪退。

下面是解决后的案例代码F1a;

XMl:

<?xML version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.COM/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width=";match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivITy">

    <Button
        android:id="@+id/button2_1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Button"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.293"
        app:layout_constraintStart_toEndOf="@+id/textView2_1"
        app:layout_constraintTop_toTopOf="@+id/textView2_1" />

    <TextView
        android:id="@+id/textView2_1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="TextView"
        android:textSize="24sp"
        app:layout_constraintBottom_toTopOf="@+id/guideline2"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.292"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="0.506" />

    <androidx.constraintlayout.widget.Guideline
        android:id="@+id/guideline2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:orientation="horizontal"
        app:layout_constraintGuide_PErcent="0.15731874" />

    <LinearLayout
        android:layout_width="0dp"
        android:layout_height="0dp"
        android:orientation="vertical"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="@+id/guideline2">

        <ListView
            android:id="@+id/listView2_1"
            android:layout_width="match_parent"
            android:layout_height="match_parent" />
    </LinearLayout>
</androidx.constraintlayout.widget.ConstraintLayout>

activity段：

package com.example.listviewtest;

import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;
import android.view.View;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.ListView;
import android.widget.TextView;

import java.util.ArrayList;
import java.util.List;


public class MainActivity2 extends AppCompatActivity implements View.OnClickListener {
    PRivate Button button1;
    private TextView textView1;
    private ListView listView1;
    private String[] str1=new String[] {
            "aaaaa","bbbb","cccc","ddddd",
            "sDFsf","eeeee","ffff","sdfdsfsd",
            "sdfsfdsf","QQqqq","sdfkskf","lllll"
    };
    private ArrayAdapter adapter;

    @override
    protected void onCreate(Bundle savedInstancestate) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main2);

        button1=findViewById(R.id.button2_1);
        textView1=findViewById(R.id.textView2_1);
        listView1=findViewById(R.id.listView2_1);
        getListViewData();
        button1.setOnClickListener(this);


    }

    @Override
    public void onClick(View v) {
        int id=v.getId();
        switch (id){
            case R.id.button2_1:
                finish();
                break;
        }
    }

    public void getListViewData(){
        List<String> tt=new ArrayList<>();
        for(int i=0;i<str1.length;i++) tt.add(str1[i]);
        adapter=new ArrayAdapter(this, android.R.layout.simple_list_item_1,tt);
        listView1.setAdapter(adapter);
    }
}

实现效果如下：

希望有类似问题的老表能够有效解决。