ListView+ArrayAdapter可以几行代码实现一个简单的列表,不用再写一个复杂的继承BaseAdapter的Adapter
直接用android自带的item布局,几行代码搞定
public class MainActivity3 extends AppCompatActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main3);
final ListView listView = findViewById(R.id.list_view);
String[] items = new String[100];
for (int i = 0; i < items.length; i++) {
items[i] = "item" + i;
}
listView.setAdapter(new ArrayAdapter<>(this, android.R.layout.simple_list_item_1, items));
}
}
上面示例的数据源为数组,ArrayAdapter也支持List数据源
public class MainActivity3 extends AppCompatActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main3);
final ListView listView = findViewById(R.id.list_view);
List items = new ArrayList<>();
for (int i = 0; i < 100; i++) {
items.add("item" + i);
}
listView.setAdapter(new ArrayAdapter<>(this, android.R.layout.simple_list_item_1, items));
}
}
上面的数据都是String类型,其实ArrayList也支持自定义的数据类型,显示的内容是改对象toString的内容,所有可以重写对象的toString()方法显示要显示的内容
public class MainActivity3 extends AppCompatActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main3);
final ListView listView = findViewById(R.id.list_view);
List items = new ArrayList<>();
for (int i = 0; i < 100; i++) {
items.add(new Student("Student" + i, i));
}
listView.setAdapter(new ArrayAdapter<>(this, android.R.layout.simple_list_item_1, items));
}
private class Student {
public String name;
public int age;
public Student() {}
public Student(String name, int age) {
this.name = name;
this.age = age;
}
@Override
public String toString() {
return name + "今年" + age + "岁啦";
}
}
}
我们上面item的布局用的是android自带的布局android.R.layout.simple_list_item_1,其实我们也可以自定义布局
先看下android.R.layout.simple_list_item_1的源码
然后模仿android.R.layout.simple_list_item_1的布局文件,自定义一个布局文件item.xml
这种只有一个TextView的情况下可以不设置TextView的id
然后在在创建ArrayAdapter时传入R.layout.item即可
listView.setAdapter(new ArrayAdapter<>(this, R.layout.item, items));
需要注意的是如果是如果是一个复杂的布局,一定要指定一个android:id="@android:id/text1"的TextView来显示数据内容,否则ArrayList会默认把最外层的控件转化成TextView,导致类型转化错误,会报如下错误
2019-09-04 15:10:42.838 3838-3838/com.him.hisapp E/ArrayAdapter: You must supply a resource ID for a TextView
--------- beginning of crash
2019-09-04 15:10:42.843 3838-3838/com.him.hisapp E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.him.hisapp, PID: 3838
java.lang.IllegalStateException: ArrayAdapter requires the resource ID to be a TextView
at android.widget.ArrayAdapter.createViewFromResource(ArrayAdapter.java:401)
at android.widget.ArrayAdapter.getView(ArrayAdapter.java:371)
at android.widget.AbsListView.obtainView(AbsListView.java:2413)
at android.widget.ListView.makeAndAddView(ListView.java:1986)
at android.widget.ListView.fillDown(ListView.java:709)
at android.widget.ListView.fillFromTop(ListView.java:770)
at android.widget.ListView.layoutChildren(ListView.java:1749)
at android.widget.AbsListView.onLayout(AbsListView.java:2212)
at android.view.View.layout(View.java:17708)
at android.view.ViewGroup.layout(ViewGroup.java:5631)
at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1766)
at android.widget.LinearLayout.layoutHorizontal(LinearLayout.java:1755)
at android.widget.LinearLayout.onLayout(LinearLayout.java:1521)
at android.view.View.layout(View.java:17708)
at android.view.ViewGroup.layout(ViewGroup.java:5631)
at android.widget.FrameLayout.layoutChildren(FrameLayout.java:325)
at android.widget.FrameLayout.onLayout(FrameLayout.java:261)
at android.view.View.layout(View.java:17708)
at android.view.ViewGroup.layout(ViewGroup.java:5631)
at android.support.v7.widget.ActionBarOverlayLayout.onLayout(ActionBarOverlayLayout.java:444)
at android.view.View.layout(View.java:17708)
at android.view.ViewGroup.layout(ViewGroup.java:5631)
at android.widget.FrameLayout.layoutChildren(FrameLayout.java:325)
at android.widget.FrameLayout.onLayout(FrameLayout.java:261)
at android.view.View.layout(View.java:17708)
at android.view.ViewGroup.layout(ViewGroup.java:5631)
at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1766)
at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1610)
at android.widget.LinearLayout.onLayout(LinearLayout.java:1519)
at android.view.View.layout(View.java:17708)
at android.view.ViewGroup.layout(ViewGroup.java:5631)
at android.widget.FrameLayout.layoutChildren(FrameLayout.java:325)
at android.widget.FrameLayout.onLayout(FrameLayout.java:261)
at com.android.internal.policy.DecorView.onLayout(DecorView.java:774)
at android.view.View.layout(View.java:17708)
at android.view.ViewGroup.layout(ViewGroup.java:5631)
at android.view.ViewRootImpl.performLayout(ViewRootImpl.java:2519)
at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:2234)
at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1372)
at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:6782)
at android.view.Choreographer$CallbackRecord.run(Choreographer.java:933)
at android.view.Choreographer.doCallbacks(Choreographer.java:742)
at android.view.Choreographer.doFrame(Choreographer.java:674)
at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:919)
at android.os.Handler.handleCallback(Handler.java:761)
at android.os.Handler.dispatchMessage(Handler.java:98)
at android.os.Looper.loop(Looper.java:156)
at android.app.ActivityThread.main(ActivityThread.java:6623)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:942)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:832)
Caused by: java.lang.ClassCastException: android.widget.LinearLayout cannot be cast to android.widget.TextView
at android.widget.ArrayAdapter.createViewFromResource(ArrayAdapter.java:388)
at android.widget.ArrayAdapter.getView(ArrayAdapter.java:371)
at android.widget.AbsListView.obtainView(AbsListView.java:2413)
at android.widget.ListView.makeAndAddView(ListView.java:1986)
at android.widget.ListView.fillDown(ListView.java:709)
at android.widget.ListView.fillFromTop(ListView.java:770)
at android.widget.ListView.layoutChildren(ListView.java:1749)
at android.widget.AbsListView.onLayout(AbsListView.java:2212)
at android.view.View.layout(View.java:17708)
at android.view.ViewGroup.layout(ViewGroup.java:5631)
at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1766)
at android.widget.LinearLayout.layoutHorizontal(LinearLayout.java:1755)
at android.widget.LinearLayout.onLayout(LinearLayout.java:1521)
at android.view.View.layout(View.java:17708)
at android.view.ViewGroup.layout(ViewGroup.java:5631)
at android.widget.FrameLayout.layoutChildren(FrameLayout.java:325)
at android.widget.FrameLayout.onLayout(FrameLayout.java:261)
at android.view.View.layout(View.java:17708)
at android.view.ViewGroup.layout(ViewGroup.java:5631)
at android.support.v7.widget.ActionBarOverlayLayout.onLayout(ActionBarOverlayLayout.java:444)
at android.view.View.layout(View.java:17708)
at android.view.ViewGroup.layout(ViewGroup.java:5631)
at android.widget.FrameLayout.layoutChildren(FrameLayout.java:325)
at android.widget.FrameLayout.onLayout(FrameLayout.java:261)
at android.view.View.layout(View.java:17708)
at android.view.ViewGroup.layout(ViewGroup.java:5631)
at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1766)
at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1610)
at android.widget.LinearLayout.onLayout(LinearLayout.java:1519)
at android.view.View.layout(View.java:17708)
at android.view.ViewGroup.layout(ViewGroup.java:5631)
at android.widget.FrameLayout.layoutChildren(FrameLayout.java:325)
at android.widget.FrameLayout.onLayout(FrameLayout.java:261)
at com.android.internal.policy.DecorView.onLayout(DecorView.java:774)
at android.view.View.layout(View.java:17708)
at android.view.ViewGroup.layout(ViewGroup.java:5631)
at android.view.ViewRootImpl.performLayout(ViewRootImpl.java:2519)
at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:2234)
at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1372)
at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:6782)
at android.view.Choreographer$CallbackRecord.run(Choreographer.java:933)
at android.view.Choreographer.doCallbacks(Choreographer.java:742)
at android.view.Choreographer.doFrame(Choreographer.java:674)
at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:919)
at android.os.Handler.handleCallback(Handler.java:761)
at android.os.Handler.dispatchMessage(Handler.java:98)
at android.os.Looper.loop(Looper.java:156)
at android.app.ActivityThread.main(ActivityThread.java:6623)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:942)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:832)