Question

我对android很新，我真的需要帮助。我正在尝试编写一些代码，使用GridView在SD卡上显示图片，但到目前为止，当我运行应用程序时，只显示顶部的textview。我想知道我的代码在主要活动代码，图像适配器类代码或两者中的逻辑是否存在严重缺陷。这是我的代码：

package com.newtestforsdcarddisplay;

import android.app.Activity;
import android.os.Bundle;
import android.database.Cursor;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.view.View;
import android.widget.GridView;
import android.widget.AdapterView;
import android.widget.Toast;
import android.provider.MediaStore;
import android.provider.MediaStore.Images.Thumbnails;
import android.net.Uri;
import android.widget.AdapterView.OnItemClickListener;


public class MainActivity extends Activity {

public Cursor myImageCursor;
public int columnNumber;



/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);

String[] imageIDs = new String[]{Thumbnails._ID};

Uri myImagesSource = MediaStore.Images.Media.EXTERNAL_CONTENT_URI;

myImageCursor = managedQuery(myImagesSource, 
                imageIDs, null, null, MediaStore.Images.Thumbnails._ID);

         columnNumber = myImageCursor.getColumnIndexOrThrow(MediaStore.Images.Media._ID);

    GridView PhoneImageView = (GridView)findViewById(R.id.sdcard);
    PhoneImageView.setAdapter(new ImageAdapter(this));

    PhoneImageView.setOnItemClickListener(new OnItemClickListener() {
         public void onItemClick(AdapterView<?> parent, View v,
int position, long id) {



              String[] data = { MediaStore.Images.Media.DATA };

             Cursor  viewImageCursor = managedQuery(
MediaStore.Images.Media.EXTERNAL_CONTENT_URI, data,
null, null, MediaStore.Images.Thumbnails._ID );
           int imageColumnIndex = viewImageCursor.getColumnIndexOrThrow(MediaStore.Images.Media.DATA);
       viewImageCursor.moveToPosition(position);
       viewImageCursor.moveToFirst();
       String filepath = viewImageCursor.getString(imageColumnIndex);
       Toast.makeText(MainActivity.this, filepath, Toast.LENGTH_LONG).show();

      Bitmap yourSelectedImage = BitmapFactory.decodeFile(filepath);

      }
   });

}       
}

package com.newtestforsdcarddisplay;



import android.content.Context;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.GridView;
import android.widget.ImageView;
import android.net.Uri;
import android.provider.MediaStore;

public class ImageAdapter extends BaseAdapter{

    final   MainActivity pca = new MainActivity();



    private Context context;

    public ImageAdapter(Context localContext) {
      //  context = localContext;
    }

    public int getCount() {
       // return pca.myImageCursor.getCount();
        return 0;
    }
    public Object getItem(int position) {
        return position;
    }
    public long getItemId(int position) {
        return position;
    }

    public View getView(int position, View convertView, ViewGroup parent) {
        ImageView picturesView;
        if (convertView == null) {
            picturesView = new ImageView(context);
            // Move cursor to current position
            pca.myImageCursor.moveToPosition(position);
            // Get the current value for the requested column
            int imageID = pca.myImageCursor.getInt(pca.columnNumber);
            // Set the content of the image based on the provided URI
            picturesView.setImageURI(Uri.withAppendedPath(
                    MediaStore.Images.Media.EXTERNAL_CONTENT_URI, "" + imageID));
            picturesView.setScaleType(ImageView.ScaleType.FIT_CENTER);
            picturesView.setPadding(8, 8, 8, 8);
            picturesView.setLayoutParams(new GridView.LayoutParams(100, 100));
        }
        else {
            picturesView = (ImageView)convertView;
        }
        return picturesView;
    }   



}


package com.newtestforsdcarddisplay;



import android.content.Context;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.GridView;
import android.widget.ImageView;
import android.net.Uri;
import android.provider.MediaStore;

public class ImageAdapter extends BaseAdapter{

    final   MainActivity pca = new MainActivity();



    private Context context;

    public ImageAdapter(Context localContext) {
      //  context = localContext;
    }

    public int getCount() {
       // return pca.myImageCursor.getCount();
        return 0;
    }
    public Object getItem(int position) {
        return position;
    }
    public long getItemId(int position) {
        return position;
    }

    public View getView(int position, View convertView, ViewGroup parent) {
        ImageView picturesView;
        if (convertView == null) {
            picturesView = new ImageView(context);
            // Move cursor to current position
            pca.myImageCursor.moveToPosition(position);
            // Get the current value for the requested column
            int imageID = pca.myImageCursor.getInt(pca.columnNumber);
            // Set the content of the image based on the provided URI
            picturesView.setImageURI(Uri.withAppendedPath(
                    MediaStore.Images.Media.EXTERNAL_CONTENT_URI, "" + imageID));
            picturesView.setScaleType(ImageView.ScaleType.FIT_CENTER);
            picturesView.setPadding(8, 8, 8, 8);
            picturesView.setLayoutParams(new GridView.LayoutParams(100, 100));
        }
        else {
            picturesView = (ImageView)convertView;
        }
        return picturesView;
    }   



}

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    >
<TextView  
    android:layout_width="fill_parent" 
    android:layout_height="wrap_content" 
    android:text="@string/hello"
    />
    <GridView  
    android:id="@+id/sdcard"
    android:layout_width="fill_parent" 
    android:layout_height="fill_parent"
    android:padding="10dp"
    android:verticalSpacing="10dp"
    android:horizontalSpacing="10dp"
    android:numColumns="auto_fit"
    android:columnWidth="90dp"
    android:stretchMode="columnWidth"
    android:gravity="center"
/>


</LinearLayout>

有人可以帮我吗????正如我之前所说的，我对android很新，而且我很长时间都在努力解决这个问题。任何帮助都会非常感激。

Answer 1

这个问题你还需要帮助吗？

我要做的是像这样创建一个“根”布局

    <?xml version="1.0" encoding="utf-8"?>
    <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
      android:orientation="vertical"
      android:layout_width="fill_parent"
      android:layout_height="fill_parent">
    <include layout="@layout/my_header"/>
    <include layout="@layout/my_grid"/>      
    </LinearLayout>

在my_header.xml中，只需将文本视图设置为线性布局。

    <?xml version="1.0" encoding="utf-8"?>
    <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android">
    <TextView  
      android:layout_width="fill_parent" 
      android:layout_height="wrap_content" 
      android:text="@string/hello"
    />
    </LinearLayout>

然后在my_grid.xml中，设置gridview

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

祝你好运

Answer 2

您的getCount()返回0.我认为您应该返回myImageCursor.getCount()

您可以将构造函数更改为

ImageAdapter(Context ctx,Cursor cr)
{
this.context=ctx;
this.cursor=cr;
}

然后在适配器的cr.getCount()

中使用getCount()

使用Gridview显示存储在SD卡上的图像

2 个答案: