Question

我尝试创建一个简单的列表视图。我做了很多次＆amp;这是我第一次遇到这样的错误。在Eclipse Luna＆amp; amp;靛青。两者都有相同的错误。

这是我创建适配器瞬间的地方：

import java.util.ArrayList;
import android.app.Activity;
import android.os.Bundle;
import android.widget.ListView;


public class ActivityMain extends Activity {
public ArrayList<StructRemedy> remedies = new ArrayList<StructRemedy>();
private ListView               lstContent;
public AdapterRemedy           adapter;


@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    lstContent = (ListView) findViewById(R.id.lstContent);
    adapter = new AdapterRemedy(remedies);
    randomPopulation();
    lstContent.setAdapter(adapter);
}


private void randomPopulation() {
    for (int i = 0; i < 30; i++) {
        StructRemedy remedy = new StructRemedy();
        remedy.title = "Remedy" + i;
        remedy.description = "Desc" + i;
        remedy.rateValue = (float) (Math.random() * 5);
        remedy.type = "tisane";
        remedy.use = "Headaches";
        remedies.add(remedy);
    }

    adapter.notifyDataSetChanged();
}

}

现在错误日志（错误引用到我创建构造函数的行，你知道＆＃34; super＆＃34;行）：

06-08 10:03:27.875: E/AndroidRuntime(2715): FATAL EXCEPTION: main
06-08 10:03:27.875: E/AndroidRuntime(2715): java.lang.RuntimeException: Unable to start activity ComponentInfo{ahmad.azimi.app.herbal_remedies/test.test1.app.herbal_remedies.ActivityMain}: java.lang.NullPointerException
06-08 10:03:27.875: E/AndroidRuntime(2715):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2180)
06-08 10:03:27.875: E/AndroidRuntime(2715):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230)
06-08 10:03:27.875: E/AndroidRuntime(2715):     at android.app.ActivityThread.access$600(ActivityThread.java:141)
06-08 10:03:27.875: E/AndroidRuntime(2715):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234)
06-08 10:03:27.875: E/AndroidRuntime(2715):     at android.os.Handler.dispatchMessage(Handler.java:99)
06-08 10:03:27.875: E/AndroidRuntime(2715):     at android.os.Looper.loop(Looper.java:137)
06-08 10:03:27.875: E/AndroidRuntime(2715):     at android.app.ActivityThread.main(ActivityThread.java:5041)
06-08 10:03:27.875: E/AndroidRuntime(2715):     at java.lang.reflect.Method.invokeNative(Native Method)
06-08 10:03:27.875: E/AndroidRuntime(2715):     at java.lang.reflect.Method.invoke(Method.java:511)
06-08 10:03:27.875: E/AndroidRuntime(2715):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
06-08 10:03:27.875: E/AndroidRuntime(2715):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
06-08 10:03:27.875: E/AndroidRuntime(2715):     at dalvik.system.NativeStart.main(Native Method)
06-08 10:03:27.875: E/AndroidRuntime(2715): Caused by: java.lang.NullPointerException
06-08 10:03:27.875: E/AndroidRuntime(2715):     at android.widget.ArrayAdapter.init(ArrayAdapter.java:310)
06-08 10:03:27.875: E/AndroidRuntime(2715):     at android.widget.ArrayAdapter.<init>(ArrayAdapter.java:153)
06-08 10:03:27.875: E/AndroidRuntime(2715):     at test.test1.app.herbal_remedies.AdapterRemedy.<init>(AdapterRemedy.java:22)
06-08 10:03:27.875: E/AndroidRuntime(2715):     at test.test1.app.herbal_remedies.ActivityMain.onCreate(ActivityMain.java:22)
06-08 10:03:27.875: E/AndroidRuntime(2715):     at android.app.Activity.performCreate(Activity.java:5104)
06-08 10:03:27.875: E/AndroidRuntime(2715):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1080)
06-08 10:03:27.875: E/AndroidRuntime(2715):     at 
android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2144)

这是适配器：

import java.util.ArrayList;
import android.content.Intent;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.ImageView;
import android.widget.RatingBar;
import android.widget.TextView;


public class AdapterRemedy extends ArrayAdapter<StructRemedy> {

    public AdapterRemedy(ArrayList<StructRemedy> remedies) {
        super(G.context, R.layout.adapter_notes, remedies);
    }


    private static class ViewHolder {

        public TextView  txtTitle;
        public TextView  txtType;
        public TextView  txtFor;
        public RatingBar rating;
        public ViewGroup layoutRoot;
        public ImageView imgLogo;


        public ViewHolder(View view) {
            layoutRoot = (ViewGroup) view.findViewById(R.id.layoutRoot);
            txtTitle = (TextView) view.findViewById(R.id.txtTitle);
            txtType = (TextView) view.findViewById(R.id.txtType);
            txtFor = (TextView) view.findViewById(R.id.txtFor);
            rating = (RatingBar) view.findViewById(R.id.rate);
            imgLogo = (ImageView) view.findViewById(R.id.imgLogo);

        }


        public void fill(final ArrayAdapter<StructRemedy> adapter, final StructRemedy item, final int position) {
            txtTitle.setText(item.title);
            txtType.setText(item.type);
            txtFor.setText(item.use);
            rating.setRating(item.rateValue);
            //imgLogo.setImageBitmap(bm);

            layoutRoot.setOnClickListener(new OnClickListener() {

                @Override
                public void onClick(View view) {
                    Intent intent = new Intent(G.currentActivity, ActivitySelect.class);
                    intent.putExtra("POSITION", position);
                    G.currentActivity.startActivity(intent);
                }
            });

        }
    }


    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        ViewHolder holder;

        StructRemedy item = getItem(position);
        if (convertView == null) {
            convertView = G.inflater.inflate(R.layout.adapter_notes, parent, false);
            holder = new ViewHolder(convertView);
            convertView.setTag(holder);
        } else {
            holder = (ViewHolder) convertView.getTag();
        }
        holder.fill(this, item, position);
        return convertView;
    }
}

Answer 1

试试这个：

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    lstContent = (ListView) findViewById(R.id.lstContent);

    randomPopulation();
}

在randomPopulation之后放置adapter = new AdapterRemedy (remedies ) ;。或者在randomPopulation方法中设置适配器。并从randomPopulation中删除adapter.notifyDataSetchanged()。

在适配器代码中进行一些更改：

public AdapterRemedy(ArrayList<StructRemedy> remedies) {
        super(G.context, R.layout.adapter_notes, remedies);
    }

将其更改为：

public AdapterRemedy(context,ArrayList<StructRemedy> remedies) {
        super(context, R.layout.adapter_notes, remedies);
    }

在randomPopulation中：

    adapter = new AdapterRemedy(this,remedies);
    lstContent.setAdapter(adapter);
    adapter.notifyDataSetChanged();

Answer 2

更改你的onCreate（），

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);

lstContent = (ListView) findViewById(R.id.lstContent);
randomPopulation();    
adapter = new AdapterRemedy(remedies);

lstContent.setAdapter(adapter);
}

在adater初始化之前调用randomPopulation（）。删除

adapter.notifyDataSetChanged();

无法启动Activity Componentinfo（适配器构造函数）

2 个答案: