加载图片 获取屏幕宽高

package com.itheima.getimage;

import android.app.Activity;
import android.content.Intent;
import android.database.Cursor;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.BitmapFactory.Options;
import android.net.Uri;
import android.os.Bundle;
import android.view.View;
import android.view.WindowManager;
import android.widget.ImageView;

public class MainActivity extends Activity {

    private ImageView iv;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        
        iv = (ImageView) findViewById(R.id.iv);
    }
    
    public void open(View v) {
        Intent intent = new Intent(Intent.ACTION_PICK);
        intent.setType("image/*");
        startActivityForResult(intent, 100);
    }
    
    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent intent) {
        Uri uri = intent.getData();
        String path = getAbsolutePath(uri);
        Bitmap bm = getUsableBitmap(path);
        iv.setImageBitmap(bm);
        System.out.println(bm.getWidth() + ", " + bm.getHeight());
    }
    
    public String getAbsolutePath(Uri uri) {
        Cursor c = getContentResolver().query(uri, new String[] { "_data" }, null, null, null);
        c.moveToNext();
        return c.getString(0);
    }
    
    @SuppressWarnings("deprecation")
    private Bitmap getUsableBitmap(String path) {
        Options opts = new Options();
        opts.inJustDecodeBounds = true;            // 设置只加载图片大小
        BitmapFactory.decodeFile(path, opts);
        
        WindowManager manager = (WindowManager) getSystemService(WINDOW_SERVICE);
        int width = manager.getDefaultDisplay().getWidth();        // 屏幕宽度
        int height = manager.getDefaultDisplay().getHeight();    // 屏幕高度
        
        int xScale = opts.outWidth / width;
        int yScale = opts.outHeight / height;
        int scale = xScale > yScale ? xScale : yScale;    // 计算缩放比例
        
        opts.inJustDecodeBounds = false;                // 设置不只加载图片大小
        opts.inSampleSize = scale;                        // 设置缩放比例
        return BitmapFactory.decodeFile(path, opts);    // 按照设置加载图片(缩放)
    }

}