HackMD
讀取相簿縮圖
AndroidManifest.xml
向系統要求這兩個權限 READ_EXTERNAL_STORAGE 與 WRITE_EXTERNAL_STORAGE，因這兩種權限屬於 Android 規範的 danger permission，故在主程式還需要額外提供程式向user要求一次
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.myapplication">
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
<application>
...
</application>
</manifest>
activity_main.xml
建立一個 GridView 來呈現縮圖，另一個 ImageView 呈現點擊後要展開全螢幕的原圖
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools= "http://schemas.android.com/tools"
android:layout_width= "fill_parent"
android:layout_height= "fill_parent"
tools:context=".MainActivity">
<GridView
android:id= "@+id/gridView1"
android:layout_width= "fill_parent"
android:layout_height= "fill_parent"
android:gravity= "center"
android:horizontalSpacing= "1dp"
android:numColumns= "4"
android:verticalSpacing= "1dp"
>
</GridView >
<ImageView
android:id= "@+id/imageView1"
android:layout_width= "fill_parent"
android:layout_height= "fill_parent"
android:gravity= "center"
android:visibility= "gone"
android:background= "#00000000"
/>
</RelativeLayout>
item_photo.xml
針對大圖做客製化事件
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:id= "@+id/rl_item_photo"
android:layout_width="match_parent"
android:layout_height="match_parent">
<ImageView
android:id= "@+id/imageView1"
android:layout_width= "fill_parent"
android:layout_height= "fill_parent" />
</RelativeLayout>
-
MainActivity.java- 點大圖的事件（畫面變回
GridView）寫在此處 - 向user要求權限
askPermission()
- 點大圖的事件（畫面變回
package com.example.myapplication;
import androidx.annotation.NonNull;
import androidx.appcompat.app.AppCompatActivity;
import androidx.core.app.ActivityCompat;
import androidx.core.content.ContextCompat;
import android.Manifest;
import android.content.pm.PackageManager;
import android.os.Bundle;
import java.util.ArrayList;
import java.util.HashSet;
import java.util.List;
import java.util.Set;
import android.app.Activity;
import android.content.ContentResolver;
import android.database.Cursor;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.Bundle;
import android.provider.MediaStore;
import android.view.Menu;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.GridView;
import android.widget.ImageView;
import android.widget.Toast;
public class MainActivity extends AppCompatActivity {
// 自訂對應的授權代碼, 實際上要override權限相關的函式時才會使用到, 如: onRequestPermissionsResult(). 不過系統在向user要求權限時仍要填入.
private static final int REQ_PERMISSIONS = 0;
private GridView gridView;
private ImageView imageView;
private List<String> thumbs; //存放縮圖的id
private List<String> imagePaths; //存放圖片的路徑
private ImageAdapter imageAdapter; //用來顯示縮圖
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
askPermission();
gridView = (GridView) findViewById(R.id.gridView1);
imageView = (ImageView) findViewById(R.id.imageView1);
ContentResolver cr = getContentResolver();
String[] projection = {
MediaStore.Images.Media._ID, // 每個資料列唯一ID
MediaStore.Images.Media.DATA // 圖片真實路徑
};
//查詢SD卡的圖片
Cursor cursor = cr.query(
MediaStore.Images.Media.EXTERNAL_CONTENT_URI, // 圖片存放的URI
projection, // 擷取的資料欄位
null,
null,
null
);
thumbs = new ArrayList<String>();
imagePaths = new ArrayList<String>();
for (int i = 0; i < cursor.getCount(); i++) {
cursor.moveToPosition(i);
int id = cursor.getInt(cursor.getColumnIndex(MediaStore.Images.Media._ID));// ID
thumbs.add(id + "");
String filepath = cursor.getString(cursor.getColumnIndex(MediaStore.Images.Media.DATA));//抓路徑
imagePaths.add(filepath);
}
cursor.close();
imageAdapter = new ImageAdapter(MainActivity.this, thumbs);
gridView.setAdapter(imageAdapter);
imageAdapter.notifyDataSetChanged();
imageView.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
imageView.setVisibility(View.GONE);
gridView.setVisibility(View.VISIBLE);
}
});
imageView.setVisibility(View.GONE);
}
private void askPermission() {
String[] permissions = {
Manifest.permission.READ_EXTERNAL_STORAGE,
Manifest.permission.WRITE_EXTERNAL_STORAGE
};
// 建立一個Set來存放所有判斷完畢，但尚未取得的權限
Set<String> permissionsRequest = new HashSet<>();
for (String p : permissions) {
// 系統檢查您要求的權限是否有被同意
int result = ContextCompat.checkSelfPermission(this, p);
if (result != PackageManager.PERMISSION_GRANTED) {
permissionsRequest.add(p);
}
}
if (!permissionsRequest.isEmpty()) {
ActivityCompat.requestPermissions(
MainActivity.this,
permissionsRequest.toArray(new String[permissionsRequest.size()]), // 轉為String
REQ_PERMISSIONS
);
} else {
Toast.makeText(MainActivity.this, "已經拿到權限囉!", Toast.LENGTH_SHORT).show();
}
}
public void setImageView(int position){
Bitmap bm = BitmapFactory.decodeFile(imagePaths.get(position));
imageView.setImageBitmap(bm);
imageView.setVisibility(View.VISIBLE);
gridView.setVisibility(View.GONE);
}
}
ImageAdapter.java
點小圖的事件（畫面變成 ImageView）寫在此處
package com.example.myapplication;
import java.util.List;
import android.content.Context;
import android.graphics.Bitmap;
import android.provider.MediaStore;
import android.util.DisplayMetrics;
import android.view.LayoutInflater;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.GridView;
import android.widget.ImageView;
import android.widget.Toast;
public class ImageAdapter extends BaseAdapter {
private ViewGroup layout;
private Context context;
private List coll;
public ImageAdapter(Context context, List coll) {
super();
this.context = context;
this.coll = coll;
}
public View getView(final int position, View convertView, ViewGroup parent) {
LayoutInflater inflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
View rowview = inflater.inflate(R.layout.item_photo, parent, false);
layout = (ViewGroup) rowview.findViewById(R.id.rl_item_photo);
ImageView imageView = (ImageView) rowview.findViewById(R.id.imageView1);
DisplayMetrics dm = context.getResources().getDisplayMetrics();
float dd = dm.density;
float px = 25 * dd;
float screenWidth = dm.widthPixels;
int newWidth = (int) (screenWidth - px) / 4; // 一行顯示四個縮圖
layout.setLayoutParams(new GridView.LayoutParams(newWidth, newWidth));
imageView.setId(position);
// Bitmap bm = BitmapFactory.decodeFile((String)coll.get(position));
// Bitmap newBit = Bitmap.createScaledBitmap(bm, newWidth, newWidth,
// true);
// 透過id向系統取得縮圖
Bitmap bm = MediaStore.Images.Thumbnails.getThumbnail(
context.getApplicationContext().getContentResolver(),
Long.parseLong((String) coll.get(position)),
MediaStore.Images.Thumbnails.MICRO_KIND, // 縮圖有另一種類型: MediaStore.Images.Thumbnails.MINI_KIND, 此解析度高於 MICRO_KIND
null
);
imageView.setImageBitmap(bm);
imageView.setScaleType(ImageView.ScaleType.FIT_XY);
//點擊照片
imageView.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
Toast.makeText(context, "index:" + position, Toast.LENGTH_SHORT).show();
((MainActivity)context).setImageView(position);
}
});
return rowview;
}
@Override
public int getCount() {
// TODO Auto-generated method stub
return coll.size();
}
@Override
public Object getItem(int arg0) {
// TODO Auto-generated method stub
return coll.get(arg0);
}
@Override
public long getItemId(int position) {
// TODO Auto-generated method stub
return position;
}
}
