Question

这是我的mainActivity.java

package com.domore.gridviewtutorial;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.widget.GridView;

public class AndroidGridLayoutActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_android_grid_layout);
        GridView gridView=(GridView)findViewById(R.id.grid_view);
        gridView.setAdapter(new ImageAdapter(this));
    }
}

我有一个grid_layout.xml，它可以从drawable目录中看到我的所有图像

<?xml version="1.0" encoding="utf-8"?>
<GridView xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/grid_view"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:numColumns="auto_fit"
    android:columnWidth="90dp"
    android:horizontalSpacing="10dp"
    android:verticalSpacing="10dp"
    android:gravity="center"
    android:stretchMode="columnWidth" >

</GridView>

我还有一个类适配器类，它会使这个grid_layout.xml膨胀，即ImageAdapter.java

package com.domore.gridviewtutorial;

import android.content.Context;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.GridView;
import android.widget.ImageView;

/**
 * Created by MY WORLD on 11/28/2015.
 */
public class ImageAdapter extends BaseAdapter {
    private Context context;

    //Keep all images into an array
    public Integer[] mThumbIds={R.drawable.first,R.drawable.second,R.drawable.third,R.drawable.fourth,
    R.drawable.fifth,R.drawable.sixth,R.drawable.seventh,R.drawable.eighth,R.drawable.ninth,R.drawable.tenth,
    R.drawable.eleventh,R.drawable.twelth,R.drawable.thirteenth,R.drawable.fourtheenth,R.drawable.fiftheenyth};

    public ImageAdapter(Context context){
        this.context=context;
    }
    @Override
    public int getCount() {
        return mThumbIds.length;
    }

    @Override
    public Object getItem(int position) {
        return mThumbIds[position];
    }

    @Override
    public long getItemId(int position) {
        return 0;
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        ImageView imageView=new ImageView(context);
        imageView.setImageResource(mThumbIds[position]);
        imageView.setScaleType(ImageView.ScaleType.CENTER_CROP);
        imageView.setLayoutParams(new GridView.LayoutParams(70,70));
        return imageView;
    }
}

在这里完成LOGCAT

Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.GridView.setAdapter(android.widget.ListAdapter)' on a null object reference
                                                                               at com.domore.gridviewtutorial.AndroidGridLayoutActivity.onCreate(AndroidGridLayoutActivity.java:14)

任何人都可以解决这个问题吗？

Answer 1

替换此 -

singleton

with - setContentView(R.layout.activity_android_grid_layout);

您使用了错误的setContentView(R.layout.grid_layout);。

Answer 2

以下是您问题的完整解决方案

ImageAdapter类

public class ImageAdapter extends BaseAdapter {
private Context context;

// Keep all images into an array
public Integer[] mThumbIds = { R.drawable.ic_communities,
        R.drawable.ic_home, R.drawable.ic_launcher, R.drawable.ic_pages,
        R.drawable.ic_people, R.drawable.ic_people, R.drawable.ic_whats_hot };

public ImageAdapter(Context context) {
    this.context = context;
}

@Override
public int getCount() {
    return mThumbIds.length;
}

@Override
public Object getItem(int position) {
    return mThumbIds[position];
}

@Override
public long getItemId(int position) {
    return 0;
}

@Override
public View getView(int position, View convertView, ViewGroup parent) {
    ImageView imageView = new ImageView(context);
    imageView.setImageResource(mThumbIds[position]);
    imageView.setScaleType(ImageView.ScaleType.CENTER_CROP);
    imageView.setLayoutParams(new GridView.LayoutParams(70, 70));
    return imageView;
}}

将代码置于oncreate MainActivity

中

setContentView(R.layout.grid_layout.xml);// Missing this to explain
GridView gridView = (GridView) findViewById(R.id.grid_view);
gridView.setAdapter(new ImageAdapter(this));

second.xml文件

<?xml version="1.0" encoding="utf-8"?>
<GridView xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/grid_view"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:columnWidth="90dp"
android:gravity="center"
android:horizontalSpacing="10dp"
android:numColumns="auto_fit"
android:stretchMode="columnWidth"
android:verticalSpacing="10dp" >
</GridView>

这对我有用，请查看。

快乐的编码，乐于助人。

Answer 3

您已将内容视图活动设置为不同的布局

setContentView(R.layout.activity_android_grid_layout);

将其更改为

setContentView(R.layout.grid_layout.xml);

包括网格布局所在的布局。

我想在Android中将我的照片设置为gridview？

3 个答案: