Gallery's image browsing and component learning

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【 experiment Purpose 】

master Gallery How to use control .

【 Experimental principle 】

1．Gallery Control

Gallery Is a list of pictures used to display horizontally , You can directly drag the picture with your finger to move the view left and right .Gallery Only one line can be displayed horizontally , And Gallery The pictures in the list will move left or right according to different dragging conditions , Until the last picture is displayed .

It's usually used to browse pictures , The selected option is in the middle , And can respond to events to display information .

2．Gallery The control of Common properties

Gallery Control commonly used XML attribute , As shown in the table 1 Shown

surface 1 Gallery frequently-used XML attribute

XML attribute	Sketch     Statement
android:animationDuration	Used to set the animation duration when switching list items
android:gravity	Used to set alignment
android:spacing	Used to set the spacing between list items
android:unselectedAlpha	Used to set the transparency of unselected list items

 

Gallery In general use Adapter Provide data to display , Usually use BaseAdapter Class is Gallery Components provide data .

 

【 The goal of the experiment 】

The goal of this experimental case is ： Picture browser

（1） stay Activity Below , adopt Gallery（ Gallery ） To display a set of pictures , You can slide the picture left and right by dragging ;

（2） When you point out a picture , This picture is enlarged and displayed in Activity Of ImageView in . Run the renderings , Pictured 1 Shown .

 

chart 1    Run the renderings

【 The experimental steps 】

1． establish The new project

First create an empty project , Such as HelloWorld project , Then make the following modifications .

 

2． Resource building

Download a set of pictures from online search , Store in drawable Under the table of contents , The names are p1.jpg、p2.jpg,... etc. .

 

3．UI Design

Modify the main layout file activity_main.xml, Add to ImageView、Gallery Components , And set its related properties , The details are as follows .

<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/activity_main"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="com.example.administrator.mygallery.MainActivity">

    <ImageView
        android:id="@+id/imageView"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        />

    <Gallery
        android:id="@+id/gallery"
        android:spacing="2dp"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_gravity="bottom"        
        />

</FrameLayout>

 

Adopt frame layout , The interface includes a ImageView And a Gallery Components ,ImageView The width of the component 、 The high attribute is set to match_parent,Gallery The alignment of components is the bottom alignment , Wide for match_parent, High for wrap_content.

 

4． Program code

This case is through BaseAdapter And Gallery Combine to complete related work . Inherited from BaseAdapter Class ImageAdapter, Among them getView in , Set up Gallery in item The width of 、 High attribute , Zoom alignment attribute .

by Gallery Set listener , When something （ picture ） When clicked , The clicked image will be filled in ImageView It shows that .

The complete code is as follows （MainActivity.java）：

 

package com.example.administrator.mygallery;

import android.content.Context;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AdapterView;
import android.widget.BaseAdapter;
import android.widget.Gallery;
import android.widget.ImageView;

public class MainActivity extends AppCompatActivity {

    int[] mImage = new int[]{R.drawable.p1, R.drawable.p2, R.drawable.p3, R.drawable.p4,
            R.drawable.p5, R.drawable.p6, R.drawable.p7, R.drawable.p8};
    ImageView image;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        image = (ImageView) findViewById(R.id.imageView);
        image.setImageResource(mImage[0]);

        Gallery gallery = (Gallery) findViewById(R.id.gallery);
        gallery.setAdapter(new ImageAdapter(this));

        gallery.setOnItemClickListener(new AdapterView.OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
                image.setImageResource(mImage[position]);
            }
        });
    }

    public class ImageAdapter extends BaseAdapter {
        Context mContext;
        public ImageAdapter(Context context) {
            mContext=context;
        }
        @Override
        public int getCount() {
            return mImage.length;
        }
        @Override
        public Object getItem(int position) {
            return mImage[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(mContext);
                imageView.setLayoutParams(new Gallery.LayoutParams(120, 120));
                imageView.setScaleType(ImageView.ScaleType.FIT_CENTER);
            }else{
                imageView=(ImageView)convertView;
            }
            imageView.setImageResource(mImage[position]);
            return imageView;
        }
    }
}

 

Program description ：

（1） Image array , That is, the picture to be displayed

int[] mImage = new int[]{R.drawable.p1, R.drawable.p2, R.drawable.p3, R.drawable.p4,
            R.drawable.p5, R.drawable.p6, R.drawable.p7, R.drawable.p8};
（2） Get ImageView object , And put a default display picture in it

image = (ImageView) findViewById(R.id.imageView);

image.setImageResource(mImage[0]);

（3） Custom inherited from BaseAdapter Class ImageAdapter class

Through this class Gallery Associate with picture data .

   

  public class ImageAdapter extends BaseAdapter {
        Context mContext;
        public ImageAdapter(Context context) {
            mContext=context;
        }
        @Override
        public int getCount() {
            return mImage.length;
        }
        @Override
        public Object getItem(int position) {
            return mImage[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(mContext);
                imageView.setLayoutParams(new Gallery.LayoutParams(120, 120));
                imageView.setScaleType(ImageView.ScaleType.FIT_CENTER);
            }else{
                imageView=(ImageView)convertView;
            }
            imageView.setImageResource(mImage[position]);
            return imageView;
        }
    }

 

The focus of this class is getView Method .

 

（4） obtain Gallery object , And connect it with ImageAdapter Object association

        Gallery gallery = (Gallery) findViewById(R.id.gallery);
        gallery.setAdapter(new ImageAdapter(this));

（5） monitor Gallery Click event , And deal with .

gallery.setOnItemClickListener(new AdapterView.OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
                image.setImageResource(mImage[position]);
            }
        });

5． Examination Syndrome effect

Compile operation , The following figure will appear 1 The effect of .

 

 

 

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