在使用GridView的片段影像 [英] Using GridView Image in Fragment
问题描述
我正在开发使用GridView控件来显示我的图片中的一类扩展片段的Android应用程序。但是,当我运行我的code,我遇到了错误。此错误显示:在GridView的setadapterNullPointerException异常。请帮帮我。我对我的英语很抱歉,这是不好的。
片段类:
公共类DetailMore扩展片段{GridView控件gridViewImage;
私人utils的utils的;
私人的ArrayList<串GT; imagePaths =新的ArrayList<串GT;();
私人GridViewImageAdapter适配器;
私人GridView控件GridView控件;
私人诠释columnWidth时;
@覆盖
公共查看onCreateView(LayoutInflater充气器,容器的ViewGroup,
捆绑savedInstanceState){ 查看查看= inflater.inflate(R.layout.detail_more,NULL); //这里创建UI组件。
gridViewImage =(GridView控件)view.findViewById(R.id.grid_view);
utils的=新utils的(getActivity()getApplicationContext()); // Initilizing网格视图
InitilizeGridLayout(); //加载从SD卡的所有图像路径
imagePaths = utils.getFilePaths(); // GridView的适配器
适配器=新GridViewImageAdapter(imagePaths,
columnWidth时); //设置网格视图适配器
尝试{
gridView.setAdapter(适配器);
}赶上(例外五){
// TODO自动生成catch块
e.printStackTrace();
}
//gridViewImage.setAdapter(new GridViewImageAdapter(活性,文件路径,imageWidth)); 返回视图。
}私人无效InitilizeGridLayout(){
资源R = getResources();
浮填充= TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP,
AppConstant.GRID_PADDING,r.getDisplayMetrics()); columnWidth时=(int)的((utils.getScreenWidth() - ((AppConstant.NUM_OF_COLUMNS + 1)*填充))/ AppConstant.NUM_OF_COLUMNS); gridViewImage.setNumColumns(AppConstant.NUM_OF_COLUMNS);
gridViewImage.setColumnWidth(columnWidth时);
gridViewImage.setStretchMode(GridView.NO_STRETCH);
gridViewImage.setPadding((INT)填充,(INT)填充,(INT)填充,
(INT)填充);
gridViewImage.setHorizontalSpacing((INT)填充);
gridViewImage.setVerticalSpacing((INT)填充);
}
}
GridViewAdapter:
公共类GridViewImageAdapter延伸BaseAdapter {
私人的ArrayList<串GT; _filePaths =新的ArrayList<串GT;();
私人诠释imageWidth;公共GridViewImageAdapter(ArrayList的<串GT;文件路径,
INT imageWidth){
this._filePaths =文件路径;
this.imageWidth = imageWidth;
}@覆盖
公众诠释的getCount(){
返回this._filePaths.size();
}@覆盖
公共对象的getItem(INT位置){
返回this._filePaths.get(位置);
}@覆盖
众长getItemId(INT位置){
返回的位置;
}@覆盖
公共查看getView(INT位置,查看convertView,父母的ViewGroup){
ImageView的ImageView的;
如果(convertView == NULL){
ImageView的=新ImageView的(_activity);
}其他{
ImageView的=(ImageView的)convertView;
} //获取屏幕尺寸
位图图像=去codeFILE(_filePaths.get(位置),imageWidth,
imageWidth); imageView.setScaleType(ImageView.ScaleType.CENTER_CROP);
imageView.setLayoutParams(新GridView.LayoutParams(imageWidth,
imageWidth));
imageView.setImageBitmap(图片);
返回ImageView的;
}
公共静态位图德codeFILE(字符串文件路径,诠释宽度,诠释HIGHT){
尝试{ 文件f =新的文件(文件路径); BitmapFactory.Options O =新BitmapFactory.Options();
o.inJustDe codeBounds = TRUE;
BitmapFactory.de codeStream(新的FileInputStream(F),空,O); 最终诠释REQUIRED_WIDTH =宽度;
最终诠释REQUIRED_HIGHT = HIGHT;
int标= 1;
而(o.outWidth /规模/ 2 - = REQUIRED_WIDTH
&功放;&安培; o.outHeight /规模/ 2 - = REQUIRED_HIGHT)
规模* = 2; BitmapFactory.Options O2 =新BitmapFactory.Options();
o2.inSampleSize =规模;
返回BitmapFactory.de codeStream(新的FileInputStream(F),空,O2);
}赶上(FileNotFoundException异常五){
e.printStackTrace();
}
返回null;
}}
AppConstant:
公共类AppConstant {//的网格视图的列数
公共静态最终诠释NUM_OF_COLUMNS = 3;// GridView的图象填补
公共静态最终诠释GRID_PADDING = 8; //在DP// SD卡图像目录
公共静态最后弦乐PHOTO_ALBUM =节;//支持的文件格式
公共静态最后的名单,LT;弦乐> FILE_EXTN = Arrays.asList(JPG,JPEG,
PNG); }
utils的:
公共类utils的{私人语境_context;//构造
公共utils的(上下文的背景下){
this._context =背景;
}//从SD卡读取文件路径
公众的ArrayList<串GT; getFilePaths(){
ArrayList的<串GT;文件路径=新的ArrayList<串GT;(); 文件目录=新的文件(
android.os.Environment.getExternalStorageDirectory()
+文件分割符+ AppConstant.PHOTO_ALBUM); //检查目录
如果(directory.isDirectory()){
//获取文件路径列表
文件[] listFiles = directory.listFiles(); //检查计数
如果(listFiles.length大于0){ //通过所有文件循环
的for(int i = 0; I< listFiles.length;我++){ //获取文件路径
字符串文件路径= listFiles [I] .getAbsolutePath(); //检查支持的文件扩展名
如果(IsSupportedFile(文件路径)){
//映像路径添加到数组列表
filePaths.add(文件路径);
}
}
}其他{
//图像目录是空的
Toast.makeText(
_context,
AppConstant.PHOTO_ALBUM
+是空的,请加载一些图像呢!
Toast.LENGTH_LONG).show();
} }其他{
AlertDialog.Builder警报=新AlertDialog.Builder(_context);
alert.setTitle(错误!);
alert.setMessage(AppConstant.PHOTO_ALBUM
+目录路径是无效的,请设置图像的目录名AppConstant.java类!);
alert.setPositiveButton(OK,NULL);
alert.show();
} 返回文件路径;
}//检查支持的文件扩展名
私人布尔IsSupportedFile(字符串文件路径){
串EXT = filePath.substring((filePath.lastIndexOf(。)+1),
filePath.length()); 如果(AppConstant.FILE_EXTN
。载(ext.toLowerCase(Locale.getDefault())))
返回true;
其他
返回false;}/ *
*让屏幕宽度
* /
@燮pressWarnings(德precation)
@燮pressLint(NewApi)
公众诠释getScreenWidth(){
INT columnWidth时;
窗口管理WM =(窗口管理器)_context
.getSystemService(Context.WINDOW_SERVICE);
显示显示= wm.getDefaultDisplay(); 最后一点点=新点();
尝试{
display.getSize(点);
}赶上(java.lang.NoSuchMethodError忽略){//旧设备
point.x = display.getWidth();
point.y = display.getHeight();
}
columnWidth时= point.x;
返回columnWidth时;
}}
detail_more.xml:
<?XML版本=1.0编码=UTF-8&GT?;
< LinearLayout中的xmlns:机器人=http://schemas.android.com/apk/res/android
机器人:layout_width =match_parent
机器人:layout_height =match_parent
机器人:方向=垂直>
< GridView控件
机器人:ID =@ + ID / grid_view
机器人:layout_width =FILL_PARENT
机器人:layout_height =FILL_PARENT
机器人:为numColumns =auto_fit
机器人:比重=中心
机器人:stretchMode =columnWidth时
机器人:背景=#000000>
< / GridView的>< / LinearLayout中>
您的GridView不被初始化,因此在 gridView.setAdapter(适配器)错误;
通话,
GridView控件GridView控件;
只声明了你的GridView,但为了使用它,你必须对其进行初始化为
的GridView =新的GridView(背景);
或
的GridView =(GridView控件)view.findViewById(你的ID);
I am developing a android app which uses a GridView to show my images in a class extends Fragment. But when I run my code, I met error. This error show: "NullPointerException" in GridView setadapter. Please help me. I sorry about my English, it is not good.
Fragment class:
public class DetailMore extends Fragment{
GridView gridViewImage;
private Utils utils;
private ArrayList<String> imagePaths = new ArrayList<String>();
private GridViewImageAdapter adapter;
private GridView gridView;
private int columnWidth;
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.detail_more, null);
// Create UI components here.
gridViewImage = (GridView)view.findViewById(R.id.grid_view);
utils = new Utils(getActivity().getApplicationContext());
// Initilizing Grid View
InitilizeGridLayout();
// loading all image paths from SD card
imagePaths = utils.getFilePaths();
// Gridview adapter
adapter = new GridViewImageAdapter(imagePaths,
columnWidth);
// setting grid view adapter
try {
gridView.setAdapter(adapter);
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
//gridViewImage.setAdapter(new GridViewImageAdapter(activity, filePaths, imageWidth));
return view;
}
private void InitilizeGridLayout() {
Resources r = getResources();
float padding = TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP,
AppConstant.GRID_PADDING, r.getDisplayMetrics());
columnWidth = (int) ((utils.getScreenWidth() - ((AppConstant.NUM_OF_COLUMNS + 1) * padding)) / AppConstant.NUM_OF_COLUMNS);
gridViewImage.setNumColumns(AppConstant.NUM_OF_COLUMNS);
gridViewImage.setColumnWidth(columnWidth);
gridViewImage.setStretchMode(GridView.NO_STRETCH);
gridViewImage.setPadding((int) padding, (int) padding, (int) padding,
(int) padding);
gridViewImage.setHorizontalSpacing((int) padding);
gridViewImage.setVerticalSpacing((int) padding);
}
}
GridViewAdapter:
public class GridViewImageAdapter extends BaseAdapter {
private ArrayList<String> _filePaths = new ArrayList<String>();
private int imageWidth;
public GridViewImageAdapter(ArrayList<String> filePaths,
int imageWidth) {
this._filePaths = filePaths;
this.imageWidth = imageWidth;
}
@Override
public int getCount() {
return this._filePaths.size();
}
@Override
public Object getItem(int position) {
return this._filePaths.get(position);
}
@Override
public long getItemId(int position) {
return position;
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
ImageView imageView;
if (convertView == null) {
imageView = new ImageView(_activity);
} else {
imageView = (ImageView) convertView;
}
// get screen dimensions
Bitmap image = decodeFile(_filePaths.get(position), imageWidth,
imageWidth);
imageView.setScaleType(ImageView.ScaleType.CENTER_CROP);
imageView.setLayoutParams(new GridView.LayoutParams(imageWidth,
imageWidth));
imageView.setImageBitmap(image);
return imageView;
}
public static Bitmap decodeFile(String filePath, int WIDTH, int HIGHT) {
try {
File f = new File(filePath);
BitmapFactory.Options o = new BitmapFactory.Options();
o.inJustDecodeBounds = true;
BitmapFactory.decodeStream(new FileInputStream(f), null, o);
final int REQUIRED_WIDTH = WIDTH;
final int REQUIRED_HIGHT = HIGHT;
int scale = 1;
while (o.outWidth / scale / 2 >= REQUIRED_WIDTH
&& o.outHeight / scale / 2 >= REQUIRED_HIGHT)
scale *= 2;
BitmapFactory.Options o2 = new BitmapFactory.Options();
o2.inSampleSize = scale;
return BitmapFactory.decodeStream(new FileInputStream(f), null, o2);
} catch (FileNotFoundException e) {
e.printStackTrace();
}
return null;
}
}
AppConstant:
public class AppConstant {
// Number of columns of Grid View
public static final int NUM_OF_COLUMNS = 3;
// Gridview image padding
public static final int GRID_PADDING = 8; // in dp
// SD card image directory
public static final String PHOTO_ALBUM = "Festival";
// supported file formats
public static final List<String> FILE_EXTN = Arrays.asList("jpg", "jpeg",
"png");
}
Utils:
public class Utils {
private Context _context;
// constructor
public Utils(Context context) {
this._context = context;
}
// Reading file paths from SDCard
public ArrayList<String> getFilePaths() {
ArrayList<String> filePaths = new ArrayList<String>();
File directory = new File(
android.os.Environment.getExternalStorageDirectory()
+ File.separator + AppConstant.PHOTO_ALBUM);
// check for directory
if (directory.isDirectory()) {
// getting list of file paths
File[] listFiles = directory.listFiles();
// Check for count
if (listFiles.length > 0) {
// loop through all files
for (int i = 0; i < listFiles.length; i++) {
// get file path
String filePath = listFiles[i].getAbsolutePath();
// check for supported file extension
if (IsSupportedFile(filePath)) {
// Add image path to array list
filePaths.add(filePath);
}
}
} else {
// image directory is empty
Toast.makeText(
_context,
AppConstant.PHOTO_ALBUM
+ " is empty. Please load some images in it !",
Toast.LENGTH_LONG).show();
}
} else {
AlertDialog.Builder alert = new AlertDialog.Builder(_context);
alert.setTitle("Error!");
alert.setMessage(AppConstant.PHOTO_ALBUM
+ " directory path is not valid! Please set the image directory name AppConstant.java class");
alert.setPositiveButton("OK", null);
alert.show();
}
return filePaths;
}
// Check supported file extensions
private boolean IsSupportedFile(String filePath) {
String ext = filePath.substring((filePath.lastIndexOf(".") + 1),
filePath.length());
if (AppConstant.FILE_EXTN
.contains(ext.toLowerCase(Locale.getDefault())))
return true;
else
return false;
}
/*
* getting screen width
*/
@SuppressWarnings("deprecation")
@SuppressLint("NewApi")
public int getScreenWidth() {
int columnWidth;
WindowManager wm = (WindowManager) _context
.getSystemService(Context.WINDOW_SERVICE);
Display display = wm.getDefaultDisplay();
final Point point = new Point();
try {
display.getSize(point);
} catch (java.lang.NoSuchMethodError ignore) { // Older device
point.x = display.getWidth();
point.y = display.getHeight();
}
columnWidth = point.x;
return columnWidth;
}
}
detail_more.xml:
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical" >
<GridView
android:id="@+id/grid_view"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:numColumns="auto_fit"
android:gravity="center"
android:stretchMode="columnWidth"
android:background="#000000">
</GridView>
</LinearLayout>
Your GridView is not initialized and hence error at gridView.setAdapter(adapter);
.
The call,
GridView gridView;
only declares your GridView, however in order to use it you must initialize it as
gridView = new GridView(context);
or
gridView = (GridView) view.findViewById(your id);
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