我正在开发一个我必须制作自定义图库的应用。为此，我必须从SD卡中搜索图像的所有图像和文件夹，并在网格视图中显示它。我的代码如下。有人请帮忙。提前谢谢。
package com.example.sdimagetutorial;
import android.app.Activity;
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.ImageView;
import android.widget.TextView;
public class GridViewAdapter extends BaseAdapter {
// Declare variables
private Activity activity;
private String[] filepath;
private String[] filename;
private static LayoutInflater inflater = null;
public GridViewAdapter(Activity a, String[] fpath, String[] fname) {
activity = a;
filepath = fpath;
filename = fname;
inflater = (LayoutInflater) activity
.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
}
public int getCount() {
return filepath.length;
}
public Object getItem(int position) {
return position;
}
public long getItemId(int position) {
return position;
}
public View getView(int position, View convertView, ViewGroup parent) {
View vi = convertView;
if (convertView == null)
vi = inflater.inflate(R.layout.gridview_item, null);
// Locate the TextView in gridview_item.xml
TextView text = (TextView) vi.findViewById(R.id.text);
// Locate the ImageView in gridview_item.xml
ImageView image = (ImageView) vi.findViewById(R.id.image);
// Set file name to the TextView followed by the position
text.setText(filename[position]);
// Decode the filepath with BitmapFactory followed by the position
Bitmap bmp = BitmapFactory.decodeFile(filepath[position]);
// Set the decoded bitmap into ImageView
image.setImageBitmap(bmp);
return vi;
}
}11-10 02:09:50.916: D/dalvikvm(28302): GC_FOR_ALLOC freed 70K, 5% free 3137K/3288K, paused 64ms, total 65ms
11-10 02:09:50.916: I/dalvikvm-heap(28302): Grow heap (frag case) to 4.209MB for 1127536-byte allocation
11-10 02:09:50.996: D/dalvikvm(28302): GC_FOR_ALLOC freed 2K, 4% free 4235K/4392K, paused 72ms, total 72ms
11-10 02:09:51.236: D/AndroidRuntime(28302): Shutting down VM
11-10 02:09:51.236: W/dalvikvm(28302): threadid=1: thread exiting with uncaught exception (group=0xb1a4aba8)
11-10 02:09:51.296: E/AndroidRuntime(28302): FATAL EXCEPTION: main
11-10 02:09:51.296: E/AndroidRuntime(28302): Process: com.example.sdimagetutorial, PID: 28302
11-10 02:09:51.296: E/AndroidRuntime(28302): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.sdimagetutorial/com.example.sdimagetutorial.MainActivity}: java.lang.NullPointerException
11-10 02:09:51.296: E/AndroidRuntime(28302): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2195)
11-10 02:09:51.296: E/AndroidRuntime(28302): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2245)
11-10 02:09:51.296: E/AndroidRuntime(28302): at android.app.ActivityThread.access$800(ActivityThread.java:135)
11-10 02:09:51.296: E/AndroidRuntime(28302): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
11-10 02:09:51.296: E/AndroidRuntime(28302): at android.os.Handler.dispatchMessage(Handler.java:102)
11-10 02:09:51.296: E/AndroidRuntime(28302): at android.os.Looper.loop(Looper.java:136)
11-10 02:09:51.296: E/AndroidRuntime(28302): at android.app.ActivityThread.main(ActivityThread.java:5017)
11-10 02:09:51.296: E/AndroidRuntime(28302): at java.lang.reflect.Method.invokeNative(Native Method)
11-10 02:09:51.296: E/AndroidRuntime(28302): at java.lang.reflect.Method.invoke(Method.java:515)
11-10 02:09:51.296: E/AndroidRuntime(28302): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
11-10 02:09:51.296: E/AndroidRuntime(28302): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
11-10 02:09:51.296: E/AndroidRuntime(28302): at dalvik.system.NativeStart.main(Native Method)
11-10 02:09:51.296: E/AndroidRuntime(28302): Caused by: java.lang.NullPointerException
11-10 02:09:51.296: E/AndroidRuntime(28302): at com.example.sdimagetutorial.MainActivity.walkdir(MainActivity.java:113)
11-10 02:09:51.296: E/AndroidRuntime(28302): at com.example.sdimagetutorial.MainActivity.onCreate(MainActivity.java:48)
11-10 02:09:51.296: E/AndroidRuntime(28302): at android.app.Activity.performCreate(Activity.java:5231)
11-10 02:09:51.296: E/AndroidRuntime(28302): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
11-10 02:09:51.296: E/AndroidRuntime(28302): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2159)
11-10 02:09:51.296: E/AndroidRuntime(28302): ... 11 morepackage com.example.sdimagetutorial;
import java.io.File;
import java.io.FileFilter;
import android.os.Bundle;
import android.os.Environment;
import android.app.Activity;
import android.content.Intent;
import android.view.View;
import android.widget.AdapterView;
import android.widget.GridView;
import android.widget.Toast;
import android.widget.AdapterView.OnItemClickListener;
public class MainActivity extends Activity {
// Declare variables
private String[] FilePathStrings;
private String[] FileNameStrings;
private File[] listFile;
GridView grid;
GridViewAdapter adapter;
File file;
String filePattent = ".jpge";
String filePattentCAP = ".JPGE";
String filePattentPNG = ".PNG";
String filePattentpng = ".png";
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
// Check for SD Card
if (!Environment.getExternalStorageState().equals(
Environment.MEDIA_MOUNTED)) {
Toast.makeText(this, "Error! No SDCARD Found!", Toast.LENGTH_LONG)
.show();
} else {
// Locate the image folder in your SD Card
file = new File(Environment.getExternalStorageDirectory()
+ File.separator + "SDImageTutorial");
// Create a new folder if no folder named SDImageTutorial exist
file.mkdirs();
}
if(file.isDirectory())
walkdir(file);
/*if (file.isDirectory()) {
listFile = file.listFiles();
// Create a String array for FilePathStrings
FilePathStrings = new String[listFile.length];
// Create a String array for FileNameStrings
FileNameStrings = new String[listFile.length];
for (int i = 0; i < listFile.length; i++) {
// Get the path of the image file
FilePathStrings[i] = listFile[i].getAbsolutePath();
// Get the name image file
FileNameStrings[i] = listFile[i].getName();
}
}
*/
// Locate the GridView in gridview_main.xml
grid = (GridView) findViewById(R.id.gridview);
// Pass String arrays to LazyAdapter Class
adapter = new GridViewAdapter(this, FilePathStrings, FileNameStrings);
// Set the LazyAdapter to the GridView
grid.setAdapter(adapter);
// Capture gridview item click
grid.setOnItemClickListener(new OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view,
int position, long id) {
Intent i = new Intent(MainActivity.this, ViewImage.class);
// Pass String arrays FilePathStrings
i.putExtra("filepath", FilePathStrings);
// Pass String arrays FileNameStrings
i.putExtra("filename", FileNameStrings);
// Pass click position
i.putExtra("position", position);
startActivity(i);
}
});
}
private void walkdir(File dir)
{
String filePattent = ".jpge";
String filePattentCAP = ".JPGE";
String filePattentPNG = ".PNG";
String filePattentpng = ".png";
File listFile[] = dir.listFiles();
if (listFile != null)
{
for (int i = 0; i < listFile.length; i++)
{
if (listFile[i].isDirectory())
{
walkdir(listFile[i]);
}
else if (listFile[i].getName().endsWith(filePattent) || listFile[i].getName().endsWith(filePattentCAP)||listFile[i].getName().endsWith(filePattentPNG) || listFile[i].getName().endsWith(filePattentpng))
{
FilePathStrings[i] = listFile[i].getAbsolutePath();
// Get the name image file
FileNameStrings[i] = listFile[i].getName();
}
}
}
}
private class ImageFileFilter implements FileFilter {
@Override
public boolean accept(File file) {
if (file.isDirectory()) {
return true;
}
else if (isImageFile(file.getAbsolutePath())) {
return true;
}
return false;
}
private boolean isImageFile(String filePath) {
if (filePath.endsWith(".jpg") || filePath.endsWith(".png"))
// Add other formats as desired
{
return true;
}
return false;
}
}
}
答案 0 :(得分：0)
你的walkdir方法（）中有一个nullpointer异常。
正如您在异常中从这一行所看到的那样：
at com.example.sdimagetutorial.MainActivity.walkdir(MainActivity.java:113)
在您的主要活动的第113行导致NPE的东西，如果您已经复制了所有代码，则为：
FilePathStrings[i] = listFile[i].getAbsolutePath();
由于您已经在前面的if条件中对listFile [i]进行了检查，这意味着FilePathStrings为null（从您的代码中看起来很可能）。
作为另一条一般建议，我想提供一些其他建议：
在执行其余循环之前添加listFile [i] .exists（）的检查 （迂腐，但有时候会有所帮助）。另外，我建议使用循环迭代器。
最重要的是，这不是写一个画廊的好方法。您 永远不应该在getView（）方法中解码位图，这是一个 真的很糟糕。看看这个例子 - http://javatechig.com/android/android-gridview-example-building-image-gallery-in-android。 基本上，每次滚动都会调用get view方法，所以如果 你去解码位图（一个非常昂贵的操作） 时间看到一个新项目，我向你保证，你的代码会导致ANR。 您应该拥有位图的持有者，并且只对它们进行一次解码， 然后从列表中获取getView中的位图（两者之一） 位图或包含位图的对象。）
答案 1 :(得分：-1)
我为sd-card图像做了Gridview标题，我在下面的链接中共享了整个项目。我希望它会有所帮助。
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