Android 点击查看大图（长按保存图片）

通常会看到点击ImageView弹出一个Dialog上面有一张大图，然后长按大图可以保存
activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout 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"
    android:padding="16dp">

    <ImageView
        android:id="@+id/image"
        android:src="@mipmap/ic_launcher"
        android:layout_centerInParent="true"
        android:layout_width="100dp"
        android:layout_height="100dp" />

</RelativeLayout>

my_dialog.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:alpha="0.5">

    <ImageView
        android:id="@+id/my_image"
        android:padding="10dp"
        android:src="@mipmap/ic_launcher"
        android:layout_width="300dp"
        android:layout_height="300dp"
        android:layout_centerVertical="true"
        android:layout_centerHorizontal="true" />

</RelativeLayout>

MainActivity.class

package visahall.cn.testsavebitmap;

import android.app.Dialog;
import android.content.DialogInterface;
import android.graphics.Bitmap;
import android.graphics.drawable.BitmapDrawable;
import android.graphics.drawable.Drawable;
import android.os.Build;
import android.os.Bundle;
import android.support.annotation.RequiresApi;
import android.support.v7.app.AlertDialog;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageView;
import android.widget.RelativeLayout;

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;

public class MainActivity extends AppCompatActivity {

    private ImageView imageView;
    private Dialog dialog;
    private ImageView mImageView;

    @RequiresApi(api = Build.VERSION_CODES.LOLLIPOP)
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        init();

        //小图的点击事件（弹出大图）
        imageView.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                dialog.show();
            }
        });

    }

    private void init() {
        imageView = (ImageView) findViewById(R.id.image);
        //大图所依附的dialog
        dialog = new Dialog(MainActivity.this, R.style.AlertDialog_AppCompat_Light_);
        mImageView = getImageView();
        dialog.setContentView(mImageView);

        //大图的点击事件（点击让他消失）
        mImageView.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                dialog.dismiss();
            }
        });

        //大图的长按监听
        mImageView.setOnLongClickListener(new View.OnLongClickListener() {
            @Override
            public boolean onLongClick(View v) {
                //弹出的“保存图片”的Dialog
                AlertDialog.Builder builder = new AlertDialog.Builder(MainActivity.this);
                builder.setItems(new String[]{getResources().getString(R.string.save_picture)}, new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialog, int which) {
                        saveCroppedImage(((BitmapDrawable) mImageView.getDrawable()).getBitmap());
                    }
                });
                builder.show();
                return true;
            }
        });
    }


    //保存图片
    private void saveCroppedImage(Bitmap bmp) {
        File file = new File("/sdcard/myFolder");
        if (!file.exists())
            file.mkdir();

        file = new File("/sdcard/temp.jpg".trim());
        String fileName = file.getName();
        String mName = fileName.substring(0, fileName.lastIndexOf("."));
        String sName = fileName.substring(fileName.lastIndexOf("."));

        // /sdcard/myFolder/temp_cropped.jpg
        String newFilePath = "/sdcard/myFolder" + "/" + mName + "_cropped" + sName;
        file = new File(newFilePath);
        try {
            file.createNewFile();
            FileOutputStream fos = new FileOutputStream(file);
            bmp.compress(Bitmap.CompressFormat.JPEG, 50, fos);
            fos.flush();
            fos.close();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

    }

    //动态的ImageView
    private ImageView getImageView(){
        ImageView iv = new ImageView(this);
        //宽高
        iv.setLayoutParams(new RelativeLayout.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.WRAP_CONTENT));
        //设置Padding
        iv.setPadding(20,20,20,20);
        //imageView设置图片
        InputStream is = getResources().openRawResource(R.mipmap.ic_launcher);
        Drawable drawable = BitmapDrawable.createFromStream(is, null);
        iv.setImageDrawable(drawable);
        return iv;
    }
}