Android下拉刷新以及GridView使用方法详解

2019-12-12 06:02:48

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GridView是类似于ListView的控件，只是GridView可以使用多个列来呈现内容，而ListView是以行为单位，所以用法上是差不多的。
主布局文件，因为要做下拉刷新，所以加了一个ProgressBar，GridView的numColumns属性是指每一行有多少列

 <RelativeLayout 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"  tools:context="com.example.girdlayoutdemo.MainActivity" >  <ProgressBar    android:id="@+id/pb"    android:layout_width="wrap_content"    android:layout_height="wrap_content"    android:layout_centerHorizontal="true" />  <GridView    android:layout_below="@id/pb"    android:id="@+id/gv"    android:layout_width="match_parent"    android:layout_height="match_parent"    android:layout_margin="5dp"    android:gravity="center"    android:numColumns="2" >  </GridView></RelativeLayout>

每个Item的布局文件，这里比较简单的一张图片加一段文字

<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"  android:layout_width="match_parent"  android:layout_height="match_parent"  android:orientation="vertical" >  <ImageView    android:id="@+id/item_iv"    android:layout_width="fill_parent"    android:layout_height="0dp"    android:layout_weight="3" />  <TextView    android:id="@+id/item_tv"    android:layout_width="match_parent"    android:layout_height="0dp"    android:layout_weight="1" /></LinearLayout>

主活动代码：

public class MainActivity extends Activity {  private GridView gv;  private ProgressBar pb;  private List<Map<String, Object>> list;  private SimpleAdapter adapter;  private GestureDetector gsDetector;  private Handler handler = new Handler() {    @Override    public void handleMessage(Message msg) {      switch (msg.what) {      case 1:        pb.setVisibility(View.GONE);        Toast.makeText(MainActivity.this, "刷新成功", 200).show();        break;      default:        break;      }    }  };  @Override  protected void onCreate(Bundle savedInstanceState) {    super.onCreate(savedInstanceState);    setContentView(R.layout.activity_main);    pb = (ProgressBar) findViewById(R.id.pb);    gv = (GridView) findViewById(R.id.gv);    pb.setVisibility(View.GONE);    initData();    adapter = new SimpleAdapter(this, list, R.layout.item_layout,        new String[] { "image", "text" }, new int[] { R.id.item_iv,            R.id.item_tv });    gv.setAdapter(adapter);    gsDetector = new GestureDetector(this, new Mlistener());    gv.setOnTouchListener(new OnTouchListener() {      @Override      public boolean onTouch(View v, MotionEvent event) {        // Log.e("MainActivity", event.getX()+"");        return gsDetector.onTouchEvent(event);      }    });  }  private void initData() {    list = new ArrayList<Map<String, Object>>();    for (int i = 0; i < 20; i++) {      Map<String, Object> map = new HashMap<String, Object>();      map.put("image", R.drawable.gift_item_default);      map.put("text", "一只冰莹猪猪");      list.add(map);    }  }  class Mlistener implements OnGestureListener {    @Override    public boolean onDown(MotionEvent e) {      return false;    }    @Override    public void onShowPress(MotionEvent e) {    }    @Override    public boolean onSingleTapUp(MotionEvent e) {      return false;    }    @Override    public boolean onScroll(MotionEvent e1, MotionEvent e2,        float distanceX, float distanceY) {      return false;    }    @Override    public void onLongPress(MotionEvent e) {    }    @Override    public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX,        float velocityY) {      if (e2.getY() - e1.getY() > 0 && gv.getFirstVisiblePosition() == 0) {        pb.setVisibility(View.VISIBLE);        Animation animation = new ScaleAnimation(1f, 1f, 0, 1f);        animation.setDuration(300);        pb.startAnimation(animation);        new Thread(new Runnable() {          @Override          public void run() {            try {              Thread.sleep(2000);              Message msg = new Message();              msg.what = 1;              handler.sendMessage(msg);            } catch (InterruptedException e) {              // TODO Auto-generated catch block              e.printStackTrace();            }          }        }).start();      }      return false;    }  }}

解析：
在onCreate方法中先获取两个组件，然后把progressBar设置为隐藏，下拉的时候再显示，刷新完毕再隐藏。然后为GridView设置数据源，这里方便起见用SimpleAdapter，然后给GridView设置ontouchListener，并在onTouch方法中把触摸事件交给我们自定义的GestureDetector对象来处理，在GestureDetector的onFling方法中处理下拉事件，在里面判断是否下拉以及GridView是否在最顶端，如果是，显示progressBar控件并开一个线程来处理刷新，这里做模拟就睡眠2000毫秒，最后用message对象返回一个消息给Handler，Handler在主线程中更新GridView。

@Override  protected void onCreate(Bundle savedInstanceState) {    super.onCreate(savedInstanceState);    setContentView(R.layout.activity_main);    pb = (ProgressBar) findViewById(R.id.pb);    gv = (GridView) findViewById(R.id.gv);    pb.setVisibility(View.GONE);    initData();    adapter = new SimpleAdapter(this, list, R.layout.item_layout,        new String[] { "image", "text" }, new int[] { R.id.item_iv,            R.id.item_tv });    gv.setAdapter(adapter);    gsDetector = new GestureDetector(this, new Mlistener());    gv.setOnTouchListener(new OnTouchListener() {      @Override      public boolean onTouch(View v, MotionEvent event) {        // Log.e("MainActivity", event.getX()+"");        return gsDetector.onTouchEvent(event);      }    });  }

class Mlistener implements OnGestureListener {    @Override    public boolean onDown(MotionEvent e) {      return false;    }    @Override    public void onShowPress(MotionEvent e) {    }    @Override    public boolean onSingleTapUp(MotionEvent e) {      return false;    }    @Override    public boolean onScroll(MotionEvent e1, MotionEvent e2,        float distanceX, float distanceY) {      return false;    }    @Override    public void onLongPress(MotionEvent e) {    }    @Override    public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX,        float velocityY) {      if (e2.getY() - e1.getY() > 0 && gv.getFirstVisiblePosition() == 0) {        pb.setVisibility(View.VISIBLE);        Animation animation = new ScaleAnimation(1f, 1f, 0, 1f);        animation.setDuration(300);        pb.startAnimation(animation);        new Thread(new Runnable() {          @Override          public void run() {            try {              Thread.sleep(2000);              Message msg = new Message();              msg.what = 1;              handler.sendMessage(msg);            } catch (InterruptedException e) {              // TODO Auto-generated catch block              e.printStackTrace();            }          }        }).start();      }      return false;    }  }

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