Android开发之杂记（3）

1，<merge/>标签

<merge />标签闪亮登场了。当LayoutInflater遇到这个标签时，它会跳过它，并将<merge />内的元素添加到<merge />的父元素里。迷惑了吗？让我们用<merge />来替换FrameLayout，并重写之前的XML布局：

<merge xmlns:android="http://schemas.android.com/apk/res/android">

    <ImageView  

        android:layout_width="fill_parent" 

        android:layout_height="fill_parent" 

        android:scaleType="center"

        android:src="@drawable/golden_gate" />

    <TextView

        android:layout_width="wrap_content" 

        android:layout_height="wrap_content" 

        android:layout_marginBottom="20dip"

        android:layout_gravity="center_horizontal|bottom"

        android:padding="12dip"

        android:background="#AA000000"

        android:textColor="#ffffffff"

        android:text="Golden Gate" />

</merge>

新的代码中，TextView和ImageView都直接添加到上一层的FrameLayout里。虽然视觉上看起来一样，但View的层次更加简单了：

很显然，在这个场合使用<merge />是因为Activity的ContentView的父元素始终是FrameLayout。如果你的布局使用LinearLayout作为它的根标签（举例），那么你就不能使用这个技巧。<merge />在其它的一些场合也很有用的。例如，它与<include />标签结合起来就能表现得很完美。你还可以在创建一个自定义的组合View时使用<merge />。让我们看一个使用<merge />创建一个新View的例子——OkCancelBar，包含两个按钮，并可以设置按钮标签。下面的XML用于在一个图片上显示自定义的View：

<merge

    xmlns:android="http://schemas.android.com/apk/res/android"    xmlns:okCancelBar="http://schemas.android.com/apk/res/com.example.android.merge">

    <ImageView  

        android:layout_width="fill_parent" 

        android:layout_height="fill_parent" 

        android:scaleType="center"

        android:src="@drawable/golden_gate" />

    <com.example.android.merge.OkCancelBar

        android:layout_width="fill_parent" 

        android:layout_height="wrap_content" 

        android:layout_gravity="bottom"

        android:paddingTop="8dip"

        android:gravity="center_horizontal"

        android:background="#AA000000"

        okCancelBar:okLabel="Save"

        okCancelBar:cancelLabel="Don't save" />

</merge>

新的布局效果如下图所示：

OkCancelBar的代码很简单，因为这两个按钮在外部的XML文件中定义，通过LayoutInflate类导入。如下面的代码片段所示，R.layout.okcancelbar以OkCancelBar为父元素：

public class OkCancelBar extends LinearLayout {

    public OkCancelBar(Context context, AttributeSet attrs) {

        super(context, attrs);

        setOrientation(HORIZONTAL);

        setGravity(Gravity.CENTER);

        setWeightSum(1.0f);

        LayoutInflater.from(context).inflate(R.layout.okcancelbar, this, true);

        TypedArray array = context.obtainStyledAttributes(attrs, R.styleable.OkCancelBar, 0, 0);

        String text = array.getString(R.styleable.OkCancelBar_okLabel);

        if (text == null) text = "Ok";

        ((Button) findViewById(R.id.okcancelbar_ok)).setText(text);

        text = array.getString(R.styleable.OkCancelBar_cancelLabel);

        if (text == null) text = "Cancel";

        ((Button) findViewById(R.id.okcancelbar_cancel)).setText(text);

        array.recycle();

    }

}

两个按钮的定义如下面的XML所示。正如你所看到的，我们使用<merge />标签直接添加两个按钮到OkCancelBar。每个按钮都是从外部相同的XML布局文件包含进来的，便于维护；我们只是简单地重写它们的id：

<merge xmlns:android="http://schemas.android.com/apk/res/android">

    <include

        layout="@layout/okcancelbar_button"

        android:id="@+id/okcancelbar_ok" />        

    <include

        layout="@layout/okcancelbar_button"

        android:id="@+id/okcancelbar_cancel" />

</merge>

我们创建了一个灵活且易于维护的自定义View，它有着高效的View层次：

<merge />标签极其有用。然而它也有以下两个限制：

·         <merge />只能作为XML布局的根标签使用

·         当Inflate以<merge />开头的布局文件时，必须指定一个父ViewGroup，并且必须设定attachToRoot为true（参看inflate(int, android.view.ViewGroup, Boolean)方法）。

2，多级下拉列表

核心类：

下载地址：http://download.csdn.net/detail/minimicall/7956483

package com.example.view;import java.util.ArrayList;import com.example.expandtabview.R;import android.app.Activity;import android.content.Context;import android.util.AttributeSet;import android.view.LayoutInflater;import android.view.View;import android.widget.LinearLayout;import android.widget.PopupWindow;import android.widget.PopupWindow.OnDismissListener;import android.widget.RelativeLayout;import android.widget.TextView;import android.widget.ToggleButton;/** * 菜单控件头部，封装了下拉动画，动态生成头部按钮个数 *  * @author yueyueniao */public class ExpandTabView extends LinearLayout implements OnDismissListener {private static final String TAG = "ExpandTabView";private ToggleButton selectedButton;private ArrayList<String> mTextArray = new ArrayList<String>();private ArrayList<RelativeLayout> mViewArray = new ArrayList<RelativeLayout>();private ArrayList<ToggleButton> mToggleButton = new ArrayList<ToggleButton>();private Context mContext;private final int SMALL = 0;private int displayWidth;private int displayHeight;private PopupWindow popupWindow;private int selectPosition;public ExpandTabView(Context context) {super(context);init(context);}public ExpandTabView(Context context, AttributeSet attrs) {super(context, attrs);init(context);}/** * 根据选择的位置设置tabitem显示的值 */public void setTitle(String valueText, int position) {if (position < mToggleButton.size()) {mToggleButton.get(position).setText(valueText);}}public void setTitle(String title){}/** * 根据选择的位置获取tabitem显示的值 */public String getTitle(int position) {if (position < mToggleButton.size() && mToggleButton.get(position).getText() != null) {return mToggleButton.get(position).getText().toString();}return "";}/** * 设置tabitem的个数和初始值 */public void setValue(ArrayList<String> textArray, ArrayList<View> viewArray) {if (mContext == null) {return;}LayoutInflater inflater = (LayoutInflater) mContext.getSystemService(Context.LAYOUT_INFLATER_SERVICE);mTextArray = textArray;for (int i = 0; i < viewArray.size(); i++) {final RelativeLayout r = new RelativeLayout(mContext);int maxHeight = (int) (displayHeight * 0.7);RelativeLayout.LayoutParams rl = new RelativeLayout.LayoutParams(RelativeLayout.LayoutParams.FILL_PARENT, maxHeight);rl.leftMargin = 10;rl.rightMargin = 10;r.addView(viewArray.get(i), rl);mViewArray.add(r);r.setTag(SMALL);ToggleButton tButton = (ToggleButton) inflater.inflate(R.layout.toggle_button, this, false);addView(tButton);View line = new TextView(mContext);line.setBackgroundResource(R.drawable.choosebar_line);if (i < viewArray.size() - 1) {LinearLayout.LayoutParams lp = new LinearLayout.LayoutParams(2, LinearLayout.LayoutParams.FILL_PARENT);addView(line, lp);}mToggleButton.add(tButton);tButton.setTag(i);tButton.setText(mTextArray.get(i));r.setOnClickListener(new OnClickListener() {@Overridepublic void onClick(View v) {onPressBack();}});r.setBackgroundColor(mContext.getResources().getColor(R.color.popup_main_background));tButton.setOnClickListener(new OnClickListener() {@Overridepublic void onClick(View view) {// initPopupWindow();ToggleButton tButton = (ToggleButton) view;if (selectedButton != null && selectedButton != tButton) {selectedButton.setChecked(false);}selectedButton = tButton;selectPosition = (Integer) selectedButton.getTag();startAnimation();if (mOnButtonClickListener != null && tButton.isChecked()) {mOnButtonClickListener.onClick(selectPosition);}}});}}private void startAnimation() {if (popupWindow == null) {popupWindow = new PopupWindow(mViewArray.get(selectPosition), displayWidth, displayHeight);popupWindow.setAnimationStyle(R.style.PopupWindowAnimation);popupWindow.setFocusable(false);popupWindow.setOutsideTouchable(true);}if (selectedButton.isChecked()) {if (!popupWindow.isShowing()) {showPopup(selectPosition);} else {popupWindow.setOnDismissListener(this);popupWindow.dismiss();hideView();}} else {if (popupWindow.isShowing()) {popupWindow.dismiss();hideView();}}}private void showPopup(int position) {View tView = mViewArray.get(selectPosition).getChildAt(0);if (tView instanceof ViewBaseAction) {ViewBaseAction f = (ViewBaseAction) tView;f.show();}if (popupWindow.getContentView() != mViewArray.get(position)) {popupWindow.setContentView(mViewArray.get(position));}popupWindow.showAsDropDown(this, 0, 0);}/** * 如果菜单成展开状态，则让菜单收回去 */public boolean onPressBack() {if (popupWindow != null && popupWindow.isShowing()) {popupWindow.dismiss();hideView();if (selectedButton != null) {selectedButton.setChecked(false);}return true;} else {return false;}}private void hideView() {View tView = mViewArray.get(selectPosition).getChildAt(0);if (tView instanceof ViewBaseAction) {ViewBaseAction f = (ViewBaseAction) tView;f.hide();}}private void init(Context context) {mContext = context;displayWidth = ((Activity) mContext).getWindowManager().getDefaultDisplay().getWidth();displayHeight = ((Activity) mContext).getWindowManager().getDefaultDisplay().getHeight();setOrientation(LinearLayout.HORIZONTAL);}@Overridepublic void onDismiss() {showPopup(selectPosition);popupWindow.setOnDismissListener(null);}private OnButtonClickListener mOnButtonClickListener;/** * 设置tabitem的点击监听事件 */public void setOnButtonClickListener(OnButtonClickListener l) {mOnButtonClickListener = l;}/** * 自定义tabitem点击回调接口 */public interface OnButtonClickListener {public void onClick(int selectPosition);}}