import android.app.Activity;
import android.graphics.Bitmap;
import android.graphics.Rect;
import android.view.View;

public class Utils {

    public static Bitmap windowShot(Activity activity) {
        // 需要截图的view
        View view = activity.getWindow().getDecorView();
        view.setDrawingCacheEnabled(true);
        view.buildDrawingCache();
        Bitmap bmp = view.getDrawingCache();
        // 获取状态栏的高度
        Rect frame = new Rect();
        activity.getWindow().getDecorView().getWindowVisibleDisplayFrame(frame);
        int statusBarHeight = frame.top;

        // 获取屏幕的宽和高
        int width = activity.getWindowManager().getDefaultDisplay().getWidth();
        int height = activity.getWindowManager().getDefaultDisplay()
                .getHeight();
        // 生成图片
        Bitmap bp = null;
            bp = Bitmap.createBitmap(bmp, 0, statusBarHeight, width, height
                    - statusBarHeight);
            view.destroyDrawingCache();
        return bp;

    }
}

import java.io.FileOutputStream;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.Locale;

import android.app.Activity;
import android.graphics.Bitmap;
import android.os.Bundle;
import android.view.Menu;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.ImageView;

public class MainActivity extends Activity {
    private Button bt;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        bt = (Button) findViewById(R.id.bt);
        bt.setOnClickListener(new OnClickListener() {

            public void onClick(View v) {

                SimpleDateFormat sdf = new SimpleDateFormat(
                        "yyyy-MM-dd_HH-mm-ss", Locale.US);
                String fname = "/sdcard/" + sdf.format(new Date()) + ".png";
                View view = v.getRootView();
                view.setDrawingCacheEnabled(true);
                view.buildDrawingCache();
                Bitmap bitmap = Utils.windowShot(MainActivity.this);
                if (bitmap != null) {
                    System.out.println("bitmap got!");
                    try {
                        FileOutputStream out = new FileOutputStream(fname);
                        bitmap.compress(Bitmap.CompressFormat.PNG, 100, out);
                        System.out.println("file " + fname + "output done.");
                    } catch (Exception e) {
                        e.printStackTrace();
                    }
                } else {
                    System.out.println("bitmap is NULL!");
                }
            }
        });
    }

}

  <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
  <uses-permission android:name="android.permission.MOUNT_UNMOUNT_FILESYSTEMS" />