我的ListView无法正常工作，它不在主页上显示listView。有解决方案吗？
也与我的布局文件有关吗？我也将在下面附加布局文件！
我正在尝试为列表视图创建适配器
这只是一个简单的一页应用程序，我尝试学习如何使用列表视图。我对代码做错了吗？我主要是在关注YouTube教程，但是仍然出现错误
MainActivity.java
package com.example.myapplication;
import android.content.res.Resources;
import android.os.Bundle;
import com.google.android.material.floatingactionbutton.FloatingActionButton;
import com.google.android.material.snackbar.Snackbar;
import androidx.appcompat.app.AppCompatActivity;
import androidx.appcompat.widget.Toolbar;
import android.view.View;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.ArrayAdapter;
import android.widget.ListView;
public class MainActivity extends AppCompatActivity {
Toolbar toolbar;
FloatingActionButton fab;
ListView myListView;
String [] items;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
toolbar = findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
Resources res = getResources();
myListView = (ListView) findViewById(R.id.myListView);
items = res.getStringArray(R.array.items);
ItemAdapter itemAdapter = new ItemAdapter(this, items);
myListView.setAdapter(itemAdapter);
// myListView.setAdapter(new ArrayAdapter<String>(this,R.layout.));
fab = findViewById(R.id.fab);
fab.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
.setAction("Action", null).show();
}
});
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.menu_main, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
//noinspection SimplifiableIfStatement
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
}
ItemAdapter.java
package com.example.myapplication;
import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.TextView;
//A class that are BaseAdapter but with another name call 'ItemAdapter'
//To pass values/data to ListView
public class ItemAdapter extends BaseAdapter {
LayoutInflater mInflater;
String[] items;
public ItemAdapter(Context c, String[] i){
items = i;
mInflater = (LayoutInflater) c.getSystemService(Context.LAYOUT_INFLATER_SERVICE); //To initialize inflater
}
@Override
public int getCount() {
return items.length;
}
@Override
public Object getItem(int i) {
return items[i];
}
@Override
public long getItemId(int i) {
return i;
}
@Override
public View getView(int i, View convertView, ViewGroup parent) {
View v = mInflater.inflate(R.layout.my_listview_details,null);
TextView nameTextView = (TextView) v.findViewById(R.id.nameTextView);
String name = items[i];
nameTextView.setText(name);
return v;
}
}
activity_main.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">
<androidx.appcompat.widget.Toolbar
android:id="@+id/toolbar"
android:layout_width="match_parent"
android:layout_height="?attr/actionBarSize"
android:background="?attr/colorPrimary"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:popupTheme="@style/AppTheme.PopupOverlay"
app:title="Your Library"
app:titleTextColor="#fff" />
<include
android:id="@+id/include"
layout="@layout/content_main"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintTop_toTopOf="parent" />
<com.google.android.material.floatingactionbutton.FloatingActionButton
android:id="@+id/fab"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginEnd="24dp"
android:layout_marginBottom="24dp"
android:clickable="true"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="1.0"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:layout_constraintVertical_bias="1.0"
app:srcCompat="@drawable/round_add_white_24" />
</androidx.constraintlayout.widget.ConstraintLayout>
content_main.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"
app:layout_behavior="@string/appbar_scrolling_view_behavior"
android:layout_marginTop="?attr/actionBarSize"
tools:context=".MainActivity"
tools:showIn="@layout/activity_main">
<ListView
android:id="@+id/myListView"
android:layout_width="0dp"
android:layout_height="0dp"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:layout_constraintVertical_bias="1.0" />
</androidx.constraintlayout.widget.ConstraintLayout>
my_listview_details.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">
<TextView
android:id="@+id/nameTextView"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentStart="true"
android:layout_alignParentTop="true"
android:layout_marginStart="24dp"
android:layout_marginTop="24dp"
android:text="TextView" />
</RelativeLayout>
任何解决方案？
而不是使用ItemAdapter一个自定义类。如果您的列表非常简单，则只需使用内置的ArrayAdapter类来注册listview。
final ArrayAdapter<String> adapter = new ArrayAdapter<String>(this,
android.R.layout.simple_list_item_1, android.R.id.text1, items);
listView.setAdapter(adapter);
用于此将高度和宽度0dp更改为如下
<ListView
android:id="@+id/myListView"
android:layout_width="match_parent"
android:layout_height="wrap_content"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:layout_constraintVertical_bias="1.0" />