Android Small Example: Use the reflection mechanism to read pictures to make a picture browser

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Project folder:

　　This example can be used for beginners ' reference exercises, if there is something wrong with it >-<

The man under the curtain

　　Java code (MAINACTIVITY.JAVA):
　　

 Packagecom.example.imageswitchtest;ImportJava.lang.reflect.Field;Importandroid.app.Activity;ImportAndroid.os.Bundle;ImportAndroid.util.Log;ImportAndroid.view.View;ImportAndroid.widget.Button;ImportAndroid.widget.ImageView;ImportAndroid.widget.Toast; Public classMainactivityextendsActivity {Private int[] IMGs =NULL;//Store Picture Address    Private intCurrentimgindex;//identification number of the current picture    PrivateImageView img =NULL ; PrivateButton Btnup =NULL ; PrivateButton Btnnext =NULL ; @Overrideprotected voidonCreate (Bundle savedinstancestate) {Super. OnCreate (savedinstancestate);                Setcontentview (R.layout.activity_main); IMG=(ImageView) Findviewbyid (r.id.img); Btnup=(Button) Findviewbyid (R.ID.BTN_UP); Btnnext=(Button) Findviewbyid (R.id.btn_next); //Initializeinit (); Img.setimageresource (imgs[1]); Currentimgindex= 1; //set Listener events for buttonBtnup.setonclicklistener (NewButtononclick ()); Btnnext.setonclicklistener (NewButtononclick ()); }       /*** Use the reflection mechanism to read the picture resources, stored in the IMGs array*/     Public voidinit () {field[] fields= R.drawable.class. GetFields ();//Reflection Read R.drawableIMGs =New int[Fields.length];//instantiating an IMGs array         for(inti = 0; i < fields.length; i++) {//traversing Fields            Try {                //the problem with the test is that the Imgs[0] value defaults to Ic_launcherLOG.D ("field[" + i + "]", fields[i].getname () + "");//Test                if(Fields[i].getname (). IndexOf ("Pic_") >-1) {//Filter the image to start with Pic_Imgs[i] = Fields[i].getint (r.drawable.class);//Gets the image storage address, stored in the IMGs arrayLOG.D ("field[" + i + "]", fields[i].getname () + "");//Test                }            } Catch(IllegalArgumentException e) {e.printstacktrace (); } Catch(illegalaccessexception e) {e.printstacktrace (); }        }    }        /**     *      * @authorBlack Sky * @ Click event Listener Processing class with Button*/    Private classButtononclickImplementsview.onclicklistener{@Override Public voidOnClick (view view) {intid = View.getid ();//Gets the component ID that the monitor hears the clicked on            Switch(ID) {//Identification ID             CaseR.ID.BTN_UP://Previous Picture button clicked on the execution method                if(currentimgindex>1) {//The current picture identification number is not the first onecurrentimgindex--;//identification number-1                                    }Else{//It's the first one .//the tip is the first pictureToast.maketext (mainactivity. This, "This is already the first picture!" ", Toast.length_short). Show (); }                 Break;  CaseR.id.btn_next://Next Picture button to click on the execution method                if(currentimgindex//The current picture identification number is not the last onecurrentimgindex++;//Identification number +1}Else{//It's the last one .//tip is the last pictureToast.maketext (mainactivity. This, "This is the last picture!" ", Toast.length_short). Show (); }                 Break; } img.setimageresource (Imgs[currentimgindex]);//Show Pictures        }            }    }

　　XML code (ACTIVITY_MAIN.XML):

<LinearLayoutxmlns: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"Android:paddingbottom= "@dimen/activity_vertical_margin"Android:paddingleft= "@dimen/activity_horizontal_margin"Android:paddingright= "@dimen/activity_horizontal_margin"Android:paddingtop= "@dimen/activity_vertical_margin"Tools:context= "Com.example.imageswitchtest.MainActivity" >    <ImageViewAndroid:id= "@+id/img"Android:layout_width= "Wrap_content"Android:layout_height= "Wrap_content"/>        <LinearLayoutAndroid:layout_width= "Match_parent"Android:layout_height= "Wrap_content"android:gravity= "Center">        <ButtonAndroid:id= "@+id/btn_up"Android:layout_width= "Wrap_content"Android:layout_height= "Wrap_content"Android:text= "Previous Picture"/>        <ButtonAndroid:id= "@+id/btn_next"Android:layout_width= "Wrap_content"Android:layout_height= "Wrap_content"Android:text= "Next Picture"/>    </LinearLayout></LinearLayout>

　　

　　Example download links are:https://files.cnblogs.com/files/hmxin/ReadBookProject.zip

Android Small Example: Use the reflection mechanism to read pictures to make a picture browser