<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"
tools:context=".MainActivity" >
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:onClick="load"
android:text="加载图片到内存" />
<ImageView
android:id="@+id/iv"
android:layout_width="fill_parent"
android:layout_height="fill_parent" />
</LinearLayout>

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 load() {
Bitmap bitmap = BitmapFactory.decodeFile("/sdcard/a.jpg");
iv.setImageBitmap(bitmap);
}
}

BitmapFactory.Options opts = new Options();
// 不去解析图片信息，只是得到图片的头部信息 宽高
opts.inJustDecodeBounds = true;

BitmapFactory.decodeFile("/sdcard/a.jpg", opts);
int imageHeight = opts.outHeight;
int imagewidth = opts.outWidth;
System.out.println("图片宽：" + imagewidth);
System.out.println("图片高" + imageHeight);

//得到手机屏幕的宽高
WindowManager wm = (WindowManager)getSystemService(WINDOW_SERVICE);
int height = wm.getDefaultDisplay().getHeight();
int width = wm.getDefaultDisplay().getWidth();

// 得到手机屏幕的宽高
WindowManager wm = (WindowManager) getSystemService(WINDOW_SERVICE);
Point outSize = new Point();
wm.getDefaultDisplay().getSize(outSize); // 3.0以后的版本才能使用

package com.wuyudong.loadimage;
import android.os.Bundle;
import android.annotation.SuppressLint;
import android.app.Activity;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.BitmapFactory.Options;
import android.graphics.Point;
import android.view.Menu;
import android.view.View;
import android.view.WindowManager;
import android.widget.ImageView;
public class MainActivity extends Activity {
private ImageView iv;
private int windowHeight;
private int windowWidth;
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
iv = (ImageView) findViewById(R.id.iv);
// 得到手机屏幕的宽高
WindowManager wm = (WindowManager) getSystemService(WINDOW_SERVICE);
windowHeight = wm.getDefaultDisplay().getHeight();
windowWidth = wm.getDefaultDisplay().getWidth();
//Point outSize = new Point();
//wm.getDefaultDisplay().getSize(outSize); // 3.0以后的版本才能使用
//windowHeight = outSize.y;
//windowWidth = outSize.x;
}
public void load(View view) {
// Bitmap bitmap = BitmapFactory.decodeFile("/sdcard/a.jpg");
// iv.setImageBitmap(bitmap);
// 图片解析的配置
BitmapFactory.Options opts = new Options();
// 不去解析图片信息，只是得到图片的头部信息 宽高
opts.inJustDecodeBounds = true;
BitmapFactory.decodeFile("/sdcard/a.jpg", opts);
int imageHeight = opts.outHeight;
int imagewidth = opts.outWidth;
System.out.println("图片宽：" + imagewidth);
System.out.println("图片高" + imageHeight);
// 计算缩放比例
int scaleX = imagewidth / windowWidth;
int scaleY = imageHeight / windowHeight;
int scale = 1;
if (scaleX > scaleY & scaleY >= 1) {
scale = scaleX;
}
if (scaleY > scaleX & scaleX >= 1) {
scale = scaleY;
}
//解析图片
opts.inJustDecodeBounds = false;
//采样率
opts.inSampleSize = scale;
Bitmap bitmap = BitmapFactory.decodeFile("/sdcard/a.jpg", opts);
iv.setImageBitmap(bitmap);
}
}