Question

我正在尝试在我的模拟器/设备上运行Android App。

没有编译时错误，但在设备/模拟器和

上运行时应用程序崩溃

＆＃34;不幸的是，GridViewMapExample已停止＆＃34;消息ID显示在屏幕上。

MainActivity.java

<local:MyControl
  // properties
/>

的strings.xml

package com.example.gridviewmapexample;

import java.util.ArrayList;

import android.support.v7.app.ActionBarActivity;
import android.content.Context;
import android.content.Intent;
import android.content.res.Resources;
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.BaseAdapter;
import android.widget.GridView;
import android.widget.ImageView;

public class MainActivity extends ActionBarActivity {

    GridView grid;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        grid = (GridView) findViewById(R.id.gridView);// step 3
        grid.setAdapter(new NikAdapter(this));

    }

}

class Country {
    String countryName;
    int imageId;

    Country(String countryName, int imageId) {
        this.countryName = countryName;
        this.imageId = imageId;

    }
}

class NikAdapter extends BaseAdapter {
    ArrayList<Country> list;
    Context c;

    NikAdapter(Context c) {
        this.c = c;
        list = new ArrayList<Country>();
        Resources res = c.getResources();
        String[] tempCountryNames = res.getStringArray(R.array.country_names);
        int[] countryImages = { R.drawable.germany_flag, R.drawable.india_flag,
                R.drawable.italy_flag, R.drawable.norway_flag,
                R.drawable.pakistan_flag, R.drawable.saudi_arabia_flag };
        for (int i = 0; i < 6; i++) {
            Country tempCountry = new Country(tempCountryNames[i],
                    countryImages[i]);
            list.add(tempCountry);
        }
    }

    @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;
    }

    class ViewHolder {
        ImageView myImageView;

        ViewHolder(View v) {
            myImageView = (ImageView) v.findViewById(R.id.imageView);
        }
    }

    @Override
    public View getView(int i, View view, ViewGroup parent) {
        View row = view;
        ViewHolder holder = null;
        if (row == null) {
            LayoutInflater inflater = (LayoutInflater) c
                    .getSystemService(Context.LAUNCHER_APPS_SERVICE);
            row = inflater.inflate(R.layout.single_item, parent, false);
            holder = new ViewHolder(row);
            row.setTag(holder);
        } else {
            holder = (ViewHolder) row.getTag();
        }
        Country temp = list.get(i);
        holder.myImageView.setImageResource(temp.imageId);
        holder.myImageView.setTag(temp);
        return row;
    }

}

single_item.xml

<?xml version="1.0" encoding="utf-8"?>
<resources>

    <string name="app_name">GridViewMapExample</string>
    <string name="hello_world">Hello world!</string>
    <string name="action_settings">Settings</string>

     <string-array name="country_names">
        <item>Germany</item>
        <item>India</item>
        <item>Italy</item>
        <item>Norway</item>
        <item>Pakistan</item>
        <item>Saudi Arabia </item>
    </string-array>

</resources>

activity_main.xml中

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent" >

    <ImageView
        android:id="@+id/imageView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentLeft="true"
        android:layout_alignParentTop="true"
        android:src="@drawable/india_flag" />

</RelativeLayout>

我得到了以下堆栈跟踪，现在搜索了很长时间后，我仍然不知道造成它的原因。

<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"
    tools:context="com.example.gridviewmapexample.MainActivity" >

    <GridView
        android:id="@+id/gridView"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_alignParentLeft="true"
        android:layout_alignParentTop="true"
        android:columnWidth="120dp"
        android:horizontalSpacing="10dp"
        android:numColumns="auto_fit"
        android:stretchMode="spacingWidthUniform"
        android:verticalSpacing="10dp" >
    </GridView>

</RelativeLayout>

Answer 1

现在您已经发布了堆栈跟踪（顺便说一下，不需要其余日志），您应该能够找到问题发生的位置。

堆栈跟踪告诉您NPE（NullPointerException）出现在getView()的第98行的MainActivity.java。

我不知道98行是哪一行，但我发现getView()存在潜在问题：

您想要LayoutInflater，但请致电getSystemService(Context.LAUNCHER_APPS_SERVICE)。您可能想要致电getSystemService(Context.LAYOUT_INFLATER_SERVICE)。

使用GridView和BaseAdapter的Android应用程序

1 个答案: