Android下拉刷新以及GridView使用方法详解
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
<RelativeLayoutxmlns: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
<?xmlversion="1.0"encoding="utf-8"?> <LinearLayoutxmlns: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:
publicclassMainActivityextendsActivity{ privateGridViewgv; privateProgressBarpb; privateList<Map<String,Object>>list; privateSimpleAdapteradapter; privateGestureDetectorgsDetector; privateHandlerhandler=newHandler(){ @Override publicvoidhandleMessage(Messagemsg){ switch(msg.what){ case1: pb.setVisibility(View.GONE); Toast.makeText(MainActivity.this,"刷新成功",200).show(); break; default: break; } } }; @Override protectedvoidonCreate(BundlesavedInstanceState){ 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=newSimpleAdapter(this,list,R.layout.item_layout, newString[]{"image","text"},newint[]{R.id.item_iv, R.id.item_tv}); gv.setAdapter(adapter); gsDetector=newGestureDetector(this,newMlistener()); gv.setOnTouchListener(newOnTouchListener(){ @Override publicbooleanonTouch(Viewv,MotionEventevent){ //Log.e("MainActivity",event.getX()+""); returngsDetector.onTouchEvent(event); } }); } privatevoidinitData(){ list=newArrayList<Map<String,Object>>(); for(inti=0;i<20;i++){ Map<String,Object>map=newHashMap<String,Object>(); map.put("image",R.drawable.gift_item_default); map.put("text","一只冰莹猪猪"); list.add(map); } } classMlistenerimplementsOnGestureListener{ @Override publicbooleanonDown(MotionEvente){ returnfalse; } @Override publicvoidonShowPress(MotionEvente){ } @Override publicbooleanonSingleTapUp(MotionEvente){ returnfalse; } @Override publicbooleanonScroll(MotionEvente1,MotionEvente2, floatdistanceX,floatdistanceY){ returnfalse; } @Override publicvoidonLongPress(MotionEvente){ } @Override publicbooleanonFling(MotionEvente1,MotionEvente2,floatvelocityX, floatvelocityY){ if(e2.getY()-e1.getY()>0&&gv.getFirstVisiblePosition()==0){ pb.setVisibility(View.VISIBLE); Animationanimation=newScaleAnimation(1f,1f,0,1f); animation.setDuration(300); pb.startAnimation(animation); newThread(newRunnable(){ @Override publicvoidrun(){ try{ Thread.sleep(2000); Messagemsg=newMessage(); msg.what=1; handler.sendMessage(msg); }catch(InterruptedExceptione){ //TODOAuto-generatedcatchblock e.printStackTrace(); } } }).start(); } returnfalse; } } }
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 protectedvoidonCreate(BundlesavedInstanceState){ 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=newSimpleAdapter(this,list,R.layout.item_layout, newString[]{"image","text"},newint[]{R.id.item_iv, R.id.item_tv}); gv.setAdapter(adapter); gsDetector=newGestureDetector(this,newMlistener()); gv.setOnTouchListener(newOnTouchListener(){ @Override publicbooleanonTouch(Viewv,MotionEventevent){ //Log.e("MainActivity",event.getX()+""); returngsDetector.onTouchEvent(event); } }); }
classMlistenerimplementsOnGestureListener{ @Override publicbooleanonDown(MotionEvente){ returnfalse; } @Override publicvoidonShowPress(MotionEvente){ } @Override publicbooleanonSingleTapUp(MotionEvente){ returnfalse; } @Override publicbooleanonScroll(MotionEvente1,MotionEvente2, floatdistanceX,floatdistanceY){ returnfalse; } @Override publicvoidonLongPress(MotionEvente){ } @Override publicbooleanonFling(MotionEvente1,MotionEvente2,floatvelocityX, floatvelocityY){ if(e2.getY()-e1.getY()>0&&gv.getFirstVisiblePosition()==0){ pb.setVisibility(View.VISIBLE); Animationanimation=newScaleAnimation(1f,1f,0,1f); animation.setDuration(300); pb.startAnimation(animation); newThread(newRunnable(){ @Override publicvoidrun(){ try{ Thread.sleep(2000); Messagemsg=newMessage(); msg.what=1; handler.sendMessage(msg); }catch(InterruptedExceptione){ //TODOAuto-generatedcatchblock e.printStackTrace(); } } }).start(); } returnfalse; } }
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