exam-01
自定义Adpter时,出现了闪退,不知道为什么,检查了很久都没有发现问题_
/res/menu/main.xml
<?xml version="1.0" encoding="utf-8"?>
<menu xmlns:android="http://schemas.android.com/apk/res/android">
<item
android:id="@+id/id_red"
android:title="红色" />
<item
android:id="@+id/id_green"
android:title="绿色" />
<item
android:id="@+id/id_blue"
android:title="蓝色"/>
<item
android:id="@+id/id_white"
android:title="白色"/>
</menu>
/res/layout/item_layout.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="match_parent"
android:layout_height="wrap_content">
<TextView
android:id="@+id/id_listview_item"
android:layout_width="match_parent"
android:layout_height="35dp" />
</LinearLayout>
activity_main.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout 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"
android:orientation="vertical">
<LinearLayout
android:id="@+id/linearLayout"
android:layout_width="match_parent"
android:layout_height="45dp"
android:orientation="horizontal">
<EditText
android:id="@+id/id_EditText"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_weight="4"
android:hint="请输入姓名" />
<Button
android:id="@+id/id_btnAdd"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_weight="1"
android:text="添加" />
</LinearLayout>
<ListView
android:id="@+id/id_listview"
android:layout_width="match_parent"
android:layout_height="0dp"
android:layout_weight="1">
</ListView>
<TextView
android:id="@+id/id_showTextView"
android:layout_width="match_parent"
android:layout_height="30dp"
android:text="你的选择是:"/>
</LinearLayout>
MyAdapter.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.ListView;
import android.widget.TextView;
import java.util.ArrayList;
import java.util.List;
public class MyAdapter extends BaseAdapter {
private List<String> list = new ArrayList<>();
private Context context;
public MyAdapter(Context context, List<String> obj){
this.context = context;
this.list = obj;
}
@Override
public int getCount() {
return list.size();
}
@Override
public Object getItem(int position) {
return list.get(position);
}
@Override
public long getItemId(int position) {
return position;
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
View view;
ViewHolder viewHolder;
if(convertView!=null){
view = LayoutInflater.from(context).inflate(R.layout.item_layout,null);
viewHolder = new ViewHolder();
viewHolder.textView = (TextView) view.findViewById(R.id.id_listview_item);
view.setTag(viewHolder);//将ViewHolder存储在View中
}else{
view = convertView;
viewHolder = (ViewHolder) view.getTag(); //重新获取ViewHolder
}
TextView textView = view.findViewById(R.id.id_showTextView);
textView.setText("你的选择是:"+list.get(position));
return view;
}
//采用内部类ViewHolder对控件的实例进行缓存,优化ListView的运行效率
class ViewHolder{
TextView textView;
}
}
MainActivity.java
package com.example.myapplication;
import android.content.Context;
import android.content.DialogInterface;
import android.graphics.Color;
import android.support.v7.app.AlertDialog;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.BaseAdapter;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ListView;
import android.widget.TextView;
import java.util.ArrayList;
import java.util.List;
public class MainActivity extends AppCompatActivity {
private TextView textView_show;
private EditText editText_add;
private Button btn_add;
private ListView listView;
private List<String> datas = new ArrayList<>();
private MyAdapter myAdapter;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
//初始化View
initView();
datas.add("text1");
datas.add("text2");
datas.add("text3");
//初始化适配器
//myAdapter = new MyAdapter(this,datas);
final TestAdapter adapter = new TestAdapter(this,datas);
//listView绑定适配器
//final ArrayAdapter adapter = new ArrayAdapter(this,android.R.layout.simple_list_item_1,datas);
listView.setAdapter(adapter);
//Button的点击事件
btn_add.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
datas.add(editText_add.getText()+"");
editText_add.setText("");
adapter.notifyDataSetChanged();
}
});
//listView的item点击事件
listView.setOnItemLongClickListener(new AdapterView.OnItemLongClickListener() {
@Override
public boolean onItemLongClick(AdapterView<?> parent, View view, final int position, long id) {
AlertDialog.Builder builder = new AlertDialog.Builder(MainActivity.this);
builder.setTitle("提醒");
builder.setMessage("是否删除");
builder.setPositiveButton("是", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
datas.remove(position);
adapter.notifyDataSetChanged();
}
});
builder.setNegativeButton("否", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
}
});
builder.show();
return true;
}
});
}
public void initView(){
editText_add= (EditText) findViewById(R.id.id_EditText);
//textView_show = (TextView) findViewById(R.id.id_showTextView);
btn_add = (Button) findViewById(R.id.id_btnAdd);
listView = (ListView) findViewById(R.id.id_listview);
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
getMenuInflater().inflate(R.menu.main,menu);
return super.onCreateOptionsMenu(menu);
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
switch (item.getItemId()){
case R.id.id_red:
listView.setBackgroundColor(Color.RED);
break;
case R.id.id_blue:
listView.setBackgroundColor(Color.BLUE);
break;
case R.id.id_green:
listView.setBackgroundColor(Color.GREEN);
break;
case R.id.id_white:
listView.setBackgroundColor(Color.WHITE);
break;
}
return super.onOptionsItemSelected(item);
}
static class TestAdapter extends BaseAdapter {
private List<String> list;
private Context context;
public TestAdapter(Context context, List<String> objects){
this.context = context;
this.list = objects;
}
@Override
public int getCount() {
return list.size();
}
@Override
public Object getItem(int i) {
return list.get(i);
}
@Override
public long getItemId(int i) {
return i;
}
@Override
public View getView(int i, View view, ViewGroup viewGroup) {
View v;
if (view == null)
{
v = LayoutInflater.from(context).inflate(R.layout.item_layout,null);
}
else {
v = view;
}
String s = list.get(i);
TextView textView = v.findViewById(R.id.id_showTextView);
textView.setText(s+"");
return v;
}
}
}
努力做最期待的自己。