Java 更新RecyclerView中的数据
我有FirstscreenActivity，在其中我使用RecyclerView（在这个RecyclerView中显示用户创建的项目的图片），然后用户进入下一个活动，在那里他创建了新项目并在那里添加了图片。当用户返回到FirstScreenActivity时，旧项目会再次下载，然后再下载新项目。 如何使旧项目在更改活动后不再下载一次（这样就不会有重复的项目）Java 更新RecyclerView中的数据,java,android,android-recyclerview,adapter,Java,Android,Android Recyclerview,Adapter,我有FirstscreenActivity，在其中我使用RecyclerView（在这个RecyclerView中显示用户创建的项目的图片），然后用户进入下一个活动，在那里他创建了新项目并在那里添加了图片。当用户返回到FirstScreenActivity时，旧项目会再次下载，然后再下载新项目。 如何使旧项目在更改活动后不再下载一次（这样就不会有重复的项目） 公共类FirstscreenActivity扩展AppCompativeActivity实现RecyclerItemClickListen
公共类FirstscreenActivity扩展AppCompativeActivity实现RecyclerItemClickListener.OnItemClickListener{
私用MyAdapter mAdapter；
私人直线酒店经理；
公共静态字符串mCurrentProject=null；
回收视图列表；
静态文件[]列表文件；
静态文件[]列表文件夹；
静态int newpressed=0；
公共静态ArrayList文件夹=新建ArrayList（）；
公共静态LruCache-mMemoryCache；
公共静态文件[]listFile2；
public void getFromSdcardFolders（）{
File File=新文件（Environment.getExternalStorageDirectory（）+
“/音频、录音、图片”、“预览”）；
if（file.isDirectory（））{
listFolders=file.listFiles（）；
对于（int i=0；ipublic class MyAdapter extends RecyclerView.Adapter<MyAdapter.ViewHolder>` {
public final Activity context;
public final ArrayList<Folder> FOLDERS;
View view;
public long getItemId(int position) {
return position;
}
@Override
public int getItemCount() {
Log.wtf("TAG", "Folders size: " + FOLDERS.size());
return FOLDERS.size();
}
// optimisation of bitmap
public static int calculateInSampleSize(
BitmapFactory.Options options, int reqWidth, int reqHeight) {
// Raw height and width of image
final int height = options.outHeight;
final int width = options.outWidth;
int inSampleSize = 1;
if (height > reqHeight || width > reqWidth) {
final int halfHeight = height / 2;
final int halfWidth = width / 2;
// Calculate the largest inSampleSize value that is a power of 2 and keeps both
// height and width larger than the requested height and width.
while ((halfHeight / inSampleSize) > reqHeight
&& (halfWidth / inSampleSize) > reqWidth) {
inSampleSize *= 2;
}
}
return inSampleSize;
}
public static Bitmap decodeSampledBitmapFromResource(String path,
int reqWidth, int reqHeight) {
// First decode with inJustDecodeBounds=true to check dimensions
final BitmapFactory.Options options = new BitmapFactory.Options();
options.inJustDecodeBounds = true;
BitmapFactory.decodeFile(path, options);
// Calculate inSampleSize
options.inSampleSize = calculateInSampleSize(options, reqWidth, reqHeight);
// Decode bitmap with inSampleSize set
options.inJustDecodeBounds = false;
return BitmapFactory.decodeFile(path, options);
}
public void loadBitmap(String path, ImageView imageView, int position) {
final String imageKey = String.valueOf(path);
Bitmap bitmap = getBitmapFromMemCache(imageKey);
if (bitmap != null) {
imageView.setImageBitmap(bitmap);
} else {
bitmap = decodeSampledBitmapFromResource(path, 100, 100);
imageView.setImageBitmap(bitmap);
// BitmapWorkerTask task = new BitmapWorkerTask(imageView, position);
// task.execute(path);
}
}
public static class ViewHolder extends RecyclerView.ViewHolder {
public TextView mTextView;
public TextView title;
public ImageView image1;
ImageView image2;
ImageView image3;
ImageView image4;
ImageView image5;
TextView slides;
public ViewHolder(View v) {
super(v);
title = (TextView) v.findViewById(R.id.item);
image1 = (ImageView) v.findViewById(R.id.icon1);
image2 = (ImageView) v.findViewById(R.id.icon2);
image3 = (ImageView) v.findViewById(R.id.icon3);
image4 = (ImageView) v.findViewById(R.id.icon4);
image5 = (ImageView) v.findViewById(R.id.icon5);
slides = (TextView) v.findViewById(R.id.textView1);
}
}
public MyAdapter(Activity context, ArrayList<Folder> FOLDERS) {
this.context = context;
this.FOLDERS = FOLDERS;
getItemCount();
}
@Override
public MyAdapter.ViewHolder onCreateViewHolder(ViewGroup parent,
int viewType) {
Log.wtf("TAG", "OnCreateViewHolder works!!!");
view = LayoutInflater.from(parent.getContext())
.inflate(R.layout.mylist, parent, false);
ViewHolder vh = new ViewHolder(view);
return vh;
}
@Override
public void onBindViewHolder(ViewHolder holder, int position) {
Folder folder = FOLDERS.get(position);
holder.image1.setImageResource(R.drawable.placeholder);
holder.image2.setImageResource(R.drawable.placeholder);
holder.image3.setImageResource(R.drawable.placeholder);
holder.image4.setImageResource(R.drawable.placeholder);
holder.image5.setImageResource(R.drawable.placeholder);
ArrayList<String> imgs = folder.getPicturelist();
holder.title.setText(folder.getName());
BitmapFactory.Options options = new BitmapFactory.Options();
options.inPreferredConfig = Bitmap.Config.RGB_565;
options.inSampleSize = 10;
for (int i = 0; i < 5; i++) {
switch (i) {
case 0:
if (imgs.size() > i && imgs.size() != 0) {
loadBitmap(imgs.get(i), holder.image1, position);
} else {
holder.image1.setImageBitmap(null);
// holder.image1.setImageResource(R.drawable.placeholder);
}
break;
case 1:
if (imgs.size() > i && imgs.size() != 0) {
loadBitmap(imgs.get(i), holder.image2, position);
} else {
holder.image2.setImageBitmap(null);
// holder.image2.setImageResource(R.drawable.placeholder);
}
break;
case 2:
if (imgs.size() > i && imgs.size() != 0) {
loadBitmap(imgs.get(i), holder.image3, position);
} else {
holder.image3.setImageBitmap(null);
// holder.image3.setImageResource(R.drawable.placeholder);
}
break;
case 3:
if (imgs.size() > i && imgs.size() != 0) {
loadBitmap(imgs.get(i), holder.image4, position);
} else {
holder.image4.setImageBitmap(null);
// holder.image4.setImageResource(R.drawable.placeholder);
}
break;
case 4:
if (imgs.size() > i && imgs.size() != 0) {
loadBitmap(imgs.get(i), holder.image5, position);
} else {
holder.image5.setImageBitmap(null);
// holder.image5.setImageResource(R.drawable.placeholder);
}
break;
}
}
holder.slides.setText("Количество слайдов: " + imgs.size());
view.setTag(holder);
}
public Bitmap getBitmapFromMemCache(String key) {
return com.example.attracti.audiorecorderpicture.FirstscreenActivity.mMemoryCache.get(key);
}
}
公共类MyAdapter扩展了RecyclerView.Adapter`{
公共最终活动背景；
公共最终ArrayList文件夹；
视图；
公共长getItemId（int位置）{
返回位置；
}
@凌驾
public int getItemCount（）{
Log.wtf（“标记”，“文件夹大小：”+Folders.size（））；
返回文件夹。大小（）；
}
//位图的优化
公共静态整数计算示例大小(
BitmapFactory.Options选项、int reqWidth、int reqHeight）{
//图像的原始高度和宽度
最终内部高度=options.outHeight；
最终整数宽度=options.outWidth；
int inSampleSize=1；
如果（高度>要求高度| |宽度>要求宽度）{
最终int半高=高度/2；
最终整数半宽度=宽度/2；
//算大数
public class MyAdapter extends RecyclerView.Adapter<MyAdapter.ViewHolder>` {
public final Activity context;
public final ArrayList<Folder> FOLDERS;
View view;
public long getItemId(int position) {
return position;
}
@Override
public int getItemCount() {
Log.wtf("TAG", "Folders size: " + FOLDERS.size());
return FOLDERS.size();
}
// optimisation of bitmap
public static int calculateInSampleSize(
BitmapFactory.Options options, int reqWidth, int reqHeight) {
// Raw height and width of image
final int height = options.outHeight;
final int width = options.outWidth;
int inSampleSize = 1;
if (height > reqHeight || width > reqWidth) {
final int halfHeight = height / 2;
final int halfWidth = width / 2;
// Calculate the largest inSampleSize value that is a power of 2 and keeps both
// height and width larger than the requested height and width.
while ((halfHeight / inSampleSize) > reqHeight
&& (halfWidth / inSampleSize) > reqWidth) {
inSampleSize *= 2;
}
}
return inSampleSize;
}
public static Bitmap decodeSampledBitmapFromResource(String path,
int reqWidth, int reqHeight) {
// First decode with inJustDecodeBounds=true to check dimensions
final BitmapFactory.Options options = new BitmapFactory.Options();
options.inJustDecodeBounds = true;
BitmapFactory.decodeFile(path, options);
// Calculate inSampleSize
options.inSampleSize = calculateInSampleSize(options, reqWidth, reqHeight);
// Decode bitmap with inSampleSize set
options.inJustDecodeBounds = false;
return BitmapFactory.decodeFile(path, options);
}
public void loadBitmap(String path, ImageView imageView, int position) {
final String imageKey = String.valueOf(path);
Bitmap bitmap = getBitmapFromMemCache(imageKey);
if (bitmap != null) {
imageView.setImageBitmap(bitmap);
} else {
bitmap = decodeSampledBitmapFromResource(path, 100, 100);
imageView.setImageBitmap(bitmap);
// BitmapWorkerTask task = new BitmapWorkerTask(imageView, position);
// task.execute(path);
}
}
public static class ViewHolder extends RecyclerView.ViewHolder {
public TextView mTextView;
public TextView title;
public ImageView image1;
ImageView image2;
ImageView image3;
ImageView image4;
ImageView image5;
TextView slides;
public ViewHolder(View v) {
super(v);
title = (TextView) v.findViewById(R.id.item);
image1 = (ImageView) v.findViewById(R.id.icon1);
image2 = (ImageView) v.findViewById(R.id.icon2);
image3 = (ImageView) v.findViewById(R.id.icon3);
image4 = (ImageView) v.findViewById(R.id.icon4);
image5 = (ImageView) v.findViewById(R.id.icon5);
slides = (TextView) v.findViewById(R.id.textView1);
}
}
public MyAdapter(Activity context, ArrayList<Folder> FOLDERS) {
this.context = context;
this.FOLDERS = FOLDERS;
getItemCount();
}
@Override
public MyAdapter.ViewHolder onCreateViewHolder(ViewGroup parent,
int viewType) {
Log.wtf("TAG", "OnCreateViewHolder works!!!");
view = LayoutInflater.from(parent.getContext())
.inflate(R.layout.mylist, parent, false);
ViewHolder vh = new ViewHolder(view);
return vh;
}
@Override
public void onBindViewHolder(ViewHolder holder, int position) {
Folder folder = FOLDERS.get(position);
holder.image1.setImageResource(R.drawable.placeholder);
holder.image2.setImageResource(R.drawable.placeholder);
holder.image3.setImageResource(R.drawable.placeholder);
holder.image4.setImageResource(R.drawable.placeholder);
holder.image5.setImageResource(R.drawable.placeholder);
ArrayList<String> imgs = folder.getPicturelist();
holder.title.setText(folder.getName());
BitmapFactory.Options options = new BitmapFactory.Options();
options.inPreferredConfig = Bitmap.Config.RGB_565;
options.inSampleSize = 10;
for (int i = 0; i < 5; i++) {
switch (i) {
case 0:
if (imgs.size() > i && imgs.size() != 0) {
loadBitmap(imgs.get(i), holder.image1, position);
} else {
holder.image1.setImageBitmap(null);
// holder.image1.setImageResource(R.drawable.placeholder);
}
break;
case 1:
if (imgs.size() > i && imgs.size() != 0) {
loadBitmap(imgs.get(i), holder.image2, position);
} else {
holder.image2.setImageBitmap(null);
// holder.image2.setImageResource(R.drawable.placeholder);
}
break;
case 2:
if (imgs.size() > i && imgs.size() != 0) {
loadBitmap(imgs.get(i), holder.image3, position);
} else {
holder.image3.setImageBitmap(null);
// holder.image3.setImageResource(R.drawable.placeholder);
}
break;
case 3:
if (imgs.size() > i && imgs.size() != 0) {
loadBitmap(imgs.get(i), holder.image4, position);
} else {
holder.image4.setImageBitmap(null);
// holder.image4.setImageResource(R.drawable.placeholder);
}
break;
case 4:
if (imgs.size() > i && imgs.size() != 0) {
loadBitmap(imgs.get(i), holder.image5, position);
} else {
holder.image5.setImageBitmap(null);
// holder.image5.setImageResource(R.drawable.placeholder);
}
break;
}
}
holder.slides.setText("Количество слайдов: " + imgs.size());
view.setTag(holder);
}
public Bitmap getBitmapFromMemCache(String key) {
return com.example.attracti.audiorecorderpicture.FirstscreenActivity.mMemoryCache.get(key);
}
}
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.myproject">
<uses-permission android:name="android.permission.CAMERA"/>
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.RECORD_AUDIO" />
<uses-feature android:name="android.hardware.camera" />
<application
android:allowBackup="true"
android:icon="@mipmap/ic_launcher"
android:label="@string/app_name"
android:supportsRtl="true"
android:theme="@style/Theme.AppCompat.Light.NoActionBar"
android:name=".model.App"
>
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
<activity android:name=".activities.AudioRecord"
android:screenOrientation="portrait"
android:configChanges="orientation|keyboardHidden">
</activity>
<activity android:name=".activities.FirstscreenActivity">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity android:name=".activities.ViewActivity">
</activity>
</application>
</manifest>
<activity android:name=".activities.FirstscreenActivity"
android:launchMode= "singleInstance"
...