具有水平Scrollview的图库

Question

我正在尝试使用horizo​​ntalscrollview做一个简单的图像库示例并动态添加图像.我搜索了一些例子,但大多数都太复杂了.有一个简单的例子,说明如何做到这一点？

Answer 1

这是一个简单的例子,它实现了水平滚动视图,看起来像图库

这会对你有所帮助

在布局中添加Horizo​​ntalScrollView:

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent" 
    android:orientation="vertical">

    <HorizontalScrollView
        android:layout_width="match_parent"
        android:layout_height="wrap_content" >
        <LinearLayout
            android:id="@+id/mygallery"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:orientation="horizontal"
            />
    </HorizontalScrollView>

</LinearLayout>

主要Java代码:

package com.example.androidhorizontalscrollviewgallery;

import java.io.File;

import android.os.Bundle;
import android.os.Environment;
import android.app.Activity;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.view.Gravity;
import android.view.View;
import android.view.ViewGroup.LayoutParams;
import android.widget.ImageView;
import android.widget.LinearLayout;
import android.widget.Toast;

public class MainActivity extends Activity {

 LinearLayout myGallery;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        myGallery = (LinearLayout)findViewById(R.id.mygallery);

        String ExternalStorageDirectoryPath = Environment
          .getExternalStorageDirectory()
          .getAbsolutePath();

        String targetPath = ExternalStorageDirectoryPath + "/test/";

        Toast.makeText(getApplicationContext(), targetPath, Toast.LENGTH_LONG).show();
        File targetDirector = new File(targetPath);

        File[] files = targetDirector.listFiles();
        for (File file : files){
         myGallery.addView(insertPhoto(file.getAbsolutePath()));
        }    
    }

    View insertPhoto(String path){
     Bitmap bm = decodeSampledBitmapFromUri(path, 220, 220);

     LinearLayout layout = new LinearLayout(getApplicationContext());
     layout.setLayoutParams(new LayoutParams(250, 250));
     layout.setGravity(Gravity.CENTER);

     ImageView imageView = new ImageView(getApplicationContext());
     imageView.setLayoutParams(new LayoutParams(220, 220));
     imageView.setScaleType(ImageView.ScaleType.CENTER_CROP);
     imageView.setImageBitmap(bm);

     layout.addView(imageView);
     return layout;
    }

    public Bitmap decodeSampledBitmapFromUri(String path, int reqWidth, int reqHeight) {
     Bitmap bm = null;

     // 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;
     bm = BitmapFactory.decodeFile(path, options); 

     return bm;  
    }

    public 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) {
      if (width > height) {
       inSampleSize = Math.round((float)height / (float)reqHeight);   
      } else {
       inSampleSize = Math.round((float)width / (float)reqWidth);   
      }   
     }

     return inSampleSize;   
    }

}

注意:在此示例中,即使不在屏幕中,也不会删除Horizo​​ntalScrollView中的位图.因此,如果加载太多位图,将抛出java.lang.OutOfMemoryError错误!