问题遇到的现象和发生背景
想做一个list view页面，但是跳转到list view界面直接闪退，错误提示list view页面无法实例化
问题相关代码，请勿粘贴截图
.xml代码
<?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="one.YIQIlist.one_threeActivity"
android:orientation="vertical">
<RelativeLayout
android:layout_width="match_parent"
android:layout_height="60dp"
android:background="@color/blue"
android:padding="10dp">
<ImageView
android:id="@+id/info_iv_flush"
android:layout_width="28dp"
android:layout_height="33dp"
android:layout_alignParentRight="true"
android:layout_centerVertical="true"
android:layout_marginRight="9dp"
android:src="@mipmap/clear_btn" />
<ImageView
android:id="@+id/info_iv_search"
android:layout_width="28dp"
android:layout_height="33dp"
android:layout_centerVertical="true"
android:layout_marginLeft="20dp"
android:layout_marginRight="10dp"
android:layout_toLeftOf="@id/info_iv_flush"
android:src="@mipmap/search_btn" />
<EditText
android:id="@+id/info_et_search"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_centerVertical="true"
android:layout_toLeftOf="@id/info_iv_search"
android:background="@drawable/info_et_bg"
android:paddingLeft="20dp"
android:textColor="@color/white"
tools:ignore="SpeakableTextPresentCheck" />
</RelativeLayout>
<ListView
android:id="@+id/one_three_lv"
android:layout_width="match_parent"
android:layout_height="718dp"
android:divider="@color/back_line_1"
android:dividerHeight="1dp"></ListView>
</LinearLayout>
.activity
package one.YIQIlist;
import android.content.Intent;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.text.TextUtils;
import android.view.View;
import android.widget.AdapterView;
import android.widget.EditText;
import android.widget.ImageView;
import android.widget.ListView;
import android.widget.Toast;
import com.ml.sdk.R;
import java.util.ArrayList;
import java.util.List;
import one.bean.YIQIBEAN;
import one.bean.YiQiUitls;
public abstract class one_threeActivity extends AppCompatActivity implements View.OnClickListener {
EditText searchEt;
ImageView searchIv,flushIv;
ListView showlv;
// ListView内部数据源
List<YIQIBEAN>mDatas;
List<YIQIBEAN>allYIQIList;
private yiqilist_adapter adapter;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_one_three);
//查找控件
initView();
//2.找到listview对应的数据源
mDatas=new ArrayList<>();
allYIQIList = YiQiUitls.getallYIQIList();
mDatas.addAll(allYIQIList);
//3.创建适配器 BaseAdapter的子类
adapter = new yiqilist_adapter(this,mDatas);
showlv.setAdapter(adapter);//4.设置适配器
// 设置单向点击监听功能
setListener();
}
private void setListener() {
showlv.setOnItemClickListener(new AdapterView.OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
YIQIBEAN yiqiBean = mDatas.get(position);
Intent intent = new Intent(one_threeActivity.this, yiqidescActivity.class);
intent.putExtra("mingcheng", yiqiBean);
startActivity(intent);
}
});
}
private void initView() {
showlv = findViewById(R.id.one_three_lv);
searchEt = findViewById(R.id.info_et_search);
searchIv = findViewById(R.id.info_iv_search);
flushIv = findViewById(R.id.info_iv_flush);
searchIv.setOnClickListener(this);
flushIv.setOnClickListener(this);
}
@Override
public void onClick(View v) {
switch (v.getId()) {
case R.id.info_iv_flush: //刷新点击
searchEt.setText("");
mDatas.clear();
mDatas.addAll(allYIQIList);
adapter.notifyDataSetChanged();
break;
case R.id.info_iv_search: //搜索点击
// 1.获取输入内容，判断不为空
String msg = searchEt.getText().toString().trim(); //获取输入信息
if (TextUtils.isEmpty(msg)) {
Toast.makeText(this,"输入内容不能为空！",Toast.LENGTH_SHORT).show();
return;
}
// 判断所有食物列表的标题是否包含输入内容，如果包含，就添加到小集合中
List<YIQIBEAN>list = new ArrayList<>();
for (int i = 0; i < allYIQIList.size(); i++) {
String mingcheng = allYIQIList.get(i).getMingcheng();
if (mingcheng.contains(msg)) {
list.add(allYIQIList.get(i));
}
}
mDatas.clear(); // 清空ListView的适配器数据源内容
mDatas.addAll(list); // 添加新的数据到数据源中
adapter.notifyDataSetChanged(); // 提示适配器更新
break;
}
}
}
适配器代码
package one.YIQIlist;
import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.ImageView;
import android.widget.TextView;
import com.ml.sdk.R;
import java.util.List;
import one.bean.YIQIBEAN;
public class yiqilist_adapter extends BaseAdapter {
Context context;
List<YIQIBEAN>mDatas;
public yiqilist_adapter(Context context, List<YIQIBEAN> mDatas) {
this.context = context;
this.mDatas = mDatas;
}
//决定了listview列表展示的行数
@Override
public int getCount() {
return mDatas.size();
}
// 返回指定位置对应的数据
@Override
public Object getItem(int position) {
return mDatas.get(position);
}
//返回指定位置ID
@Override
public long getItemId(int position) {
return position;
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
ViewHolder holder;
if (convertView == null){
convertView = LayoutInflater.from(context).inflate(R.layout.one_three_list_lv,null);//将布局转换为view对象的方法
holder = new ViewHolder(convertView);
convertView.setTag(holder);
}else {
holder = (ViewHolder) convertView.getTag();
}
//加载控件显示内容
//获取集合指定位置的数据
YIQIBEAN YIQIbean = mDatas.get(position);
holder.bianmaTv.setText(YIQIbean.getBianma());
holder.mingchengTv.setText("仪器名称："+YIQIbean.getMingcheng());
holder.iv.setImageResource(YIQIbean.getYiqitupian());
return convertView;
}
class ViewHolder {
ImageView iv;
TextView bianmaTv, mingchengTv;
public ViewHolder(View view) {
iv = view.findViewById(R.id.three_list_iv);
bianmaTv = view.findViewById(R.id.three_list_tv_bianma);
mingchengTv = view.findViewById(R.id.three_list_tv_mingcheng);
}
}
}
运行结果及报错内容
E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.hw.modelart_demo, PID: 1631
java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.hw.modelart_demo/one.YIQIlist.one_threeActivity}: java.lang.InstantiationException: java.lang.Class<one.YIQIlist.one_threeActivity> cannot be instantiated
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3365)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3601)
at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:85)
at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135)
at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2066)
at android.os.Handler.dispatchMessage(Handler.java:106)
at android.os.Looper.loop(Looper.java:223)
at android.app.ActivityThread.main(ActivityThread.java:7656)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:592)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:947)
Caused by: java.lang.InstantiationException: java.lang.Class<one.YIQIlist.one_threeActivity> cannot be instantiated
at java.lang.Class.newInstance(Native Method)
at android.app.AppComponentFactory.instantiateActivity(AppComponentFactory.java:95)
at android.support.v4.app.CoreComponentFactory.instantiateActivity(CoreComponentFactory.java:43)
at android.app.Instrumentation.newActivity(Instrumentation.java:1253)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3353)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3601)
at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:85)
at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135)
at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2066)
at android.os.Handler.dispatchMessage(Handler.java:106)
at android.os.Looper.loop(Looper.java:223)
at android.app.ActivityThread.main(ActivityThread.java:7656)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:592)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:947)
I/Process: Sending signal. PID: 1631 SIG: 9
