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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=http://www.mamicode.com/"@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=http://www.mamicode.com/"@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
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() { @Override public void onClick(View v) { onPressBack(); } }); r.setBackgroundColor(mContext.getResources().getColor(R.color.popup_main_background)); tButton.setOnClickListener(new OnClickListener() { @Override public 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); } @Override public 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); } }
Android开发之杂记(3)