好的APP应当具备良好的交互, 最好能贴心的满足用户的需求. 而人性化的提醒就是其中之一. 某些APP中经常会看到这样的场景, 当加载内容失败, 或者获取内容失败时, 界面会变成一个可与用后交互的场景. 允许用户点击屏幕或者界面中某个按钮, 尝试重新获取内容或者检测网络连接等等. Android的ListView中有类似setEmptyView(...) 的方法, 当列表中没有数据, 就会显示该 emptyView. 但并非所有的View都有这样的接口方法, 为此我们可以自己去实现可通用的"emptyView".
这里通过简单的例子提供一种思路, 当然不是唯一的. 我们可以根据自己的想法实现各种各样的emptyView本质还是调用view.setVisibility(...).
效果图如下, 看起来好简单吧!
So 直接上代码喇!
将EmptyView封装在某个常用布局文件中, 比如RelativeLayout, 当然也可以是LinearLayout等等.
public class CustomRelativeLayout extends RelativeLayout{ public static interface RetryListener{ void retry(); } private ProgressBar progressBar = null; private Button btn_refresh = null; private TextView tv_tip = null; private boolean isNormal = true; private RetryListener retryListener = null; private final static int tvTipId = 0x1001; public CustomRelativeLayout(Context context) { this(context, null); } public CustomRelativeLayout(Context context, AttributeSet attrs) { this(context, attrs, 0); } public CustomRelativeLayout(Context context, AttributeSet attrs, int defStyle) { super(context, attrs, defStyle); } /** * 设置加载界面 */ protected void setInProgress() { if(progressBar == null) { int size = (int) TypedValue .applyDimension(TypedValue.COMPLEX_UNIT_DIP, 45, getResources().getDisplayMetrics()); progressBar = new ProgressBar(getContext()); RelativeLayout.LayoutParams lp = new RelativeLayout.LayoutParams(size,size); lp.addRule(RelativeLayout.CENTER_IN_PARENT); progressBar.setLayoutParams(lp); addView(progressBar); } if(getChildCount() > 0) { int childCount = getChildCount(); if(childCount >0) { for(int i=(childCount-1); i>=0; i--) { getChildAt(i).setVisibility(View.GONE); } } } if(btn_refresh != null) btn_refresh.setVisibility(View.GONE); if(tv_tip != null) tv_tip.setVisibility(View.GONE); progressBar.setVisibility(View.VISIBLE); } /** * 显示加载失败界面,隐藏所有正常的View元素 */ protected void setChildrenGone() { if(btn_refresh == null) { btn_refresh = new Button(getContext()); tv_tip = new TextView(getContext()); tv_tip.setText("网络连接失败"); tv_tip.setGravity(Gravity.CENTER); tv_tip.setTextSize(TypedValue.COMPLEX_UNIT_SP, 16); btn_refresh.setText("刷新"); btn_refresh.setOnClickListener(new OnClickListener() { @Override public void onClick(View v) { if(retryListener != null) { retryListener.retry(); } else { Toast.makeText(getContext(), "暂无数据", Toast.LENGTH_SHORT).show(); } } }); int btnWidth = (int)TypedValue .applyDimension(TypedValue.COMPLEX_UNIT_DIP, 80, getResources().getDisplayMetrics()); RelativeLayout.LayoutParams lp = new RelativeLayout.LayoutParams(btnWidth, LayoutParams.WRAP_CONTENT); lp.addRule(RelativeLayout.CENTER_IN_PARENT); lp.setMargins(0, 10, 0, 0); btn_refresh.setLayoutParams(lp); btn_refresh.setId(tvTipId); btn_refresh.setVisibility(View.GONE); addView(btn_refresh); RelativeLayout.LayoutParams lp_tv = new RelativeLayout.LayoutParams(LayoutParams.MATCH_PARENT, LayoutParams.WRAP_CONTENT); lp_tv.addRule(RelativeLayout.ABOVE, tvTipId); tv_tip.setLayoutParams(lp_tv); addView(tv_tip); } if(getChildCount() > 0) { int childCount = getChildCount(); if(childCount >0) { for(int i=(childCount-1); i>=0; i--) { getChildAt(i).setVisibility(View.GONE); } } } if(progressBar != null) progressBar.setVisibility(View.GONE); isNormal = false; btn_refresh.setVisibility(View.VISIBLE); tv_tip.setVisibility(View.VISIBLE); } /** * 显示正常View元素 */ protected void setChildrenVisible() { if(getChildCount() > 0) { int childCount = getChildCount(); if(childCount >0) { for(int i=(childCount-1); i>=0; i--) { getChildAt(i).setVisibility(View.VISIBLE); } } if(progressBar != null) progressBar.setVisibility(View.GONE); if(btn_refresh != null) btn_refresh.setVisibility(View.GONE); if(tv_tip != null) tv_tip.setVisibility(View.GONE); isNormal = true; } } protected boolean isNormalView() { return isNormal; } public void setRetryListener(RetryListener listener) { this.retryListener = listener; }}提供一个RetryListener接口, 作为点击 "刷新" 按钮后的事件.
然后模拟加载中并且加载失败的界面, 点击按钮后迟延3秒, 假设获取数据成功, 更新view后显示正常的界面.
public class MainActivity extends Activity { private Button btn_start = null; private static CustomRelativeLayout cuLayout = null; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); init(); } private static Handler mHandler = new Handler() { @Override public void handleMessage(Message msg) { if(msg.what == 0x1) { cuLayout.setChildrenVisible(); } else if(msg.what == 0x2) { cuLayout.setChildrenGone(); } super.handleMessage(msg); } }; private void init() { btn_start = (Button) findViewById(R.id.btn_start); cuLayout = (CustomRelativeLayout) findViewById(R.id.container); cuLayout.setRetryListener(new CustomRelativeLayout.RetryListener(){ public void retry() { cuLayout.setInProgress(); mHandler.sendEmptyMessageDelayed(0x1,3000); } }); btn_start.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { cuLayout.setChildrenGone(); } }); cuLayout.setInProgress(); mHandler.sendEmptyMessageDelayed(0x2,2000); }}布局文件:
<com.alextam.progressview.CustomRelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:tools="http://schemas.android.com/tools" android:id="@+id/container" android:layout_width="match_parent" android:layout_height="match_parent" > <RelativeLayout android:layout_width="match_parent" android:layout_height="match_parent" android:background="#FFFFFF" > <ImageView android:layout_width="match_parent" android:layout_height="250dp" android:src="@mipmap/movie" /> <Button android:id="@+id/btn_start" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_centerInParent="true" android:text="ACTION" /> </RelativeLayout></com.alextam.progressview.CustomRelativeLayout>就是这么简单喇, 相信看完后也能定制出自己喜爱的界面哦! 另外, 作为EmptyView和加载view, 并不推荐使用复杂的元素. 最好简单而好看的View元素就够了. 因为仅仅是充当辅助的作用, 轻量化, 几乎不占内存是前提.
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