Android 之自定义布局（继承控件）

就是继承已有的控件，创建新控件，保留继承的父控件的特性，并且还可以引入新特性。下面就以支持横向滑动删除列表项的自定义ListView的实现来介绍。

1、创建删除按钮布局delete_btn.xml，这个布局是在横向滑动列表项后显示的：

<?xml version="1.0" encoding="utf-8"?>
<Button xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:background="#FF0000"
android:padding="5dp"
android:text="\u5220\u9664"
android:textColor="#FFFFFF"
android:textSize="16sp" >

</Button>

2、创建CustomListView类，继承自ListView，并实现了OnTouchListener和OnGestureListener接口：

package cn.com.tcl.customlistview;

import android.content.Context;
import android.util.AttributeSet;
import android.util.Log;
import android.view.GestureDetector;
import android.view.LayoutInflater;
import android.view.MotionEvent;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ListView;
import android.widget.RelativeLayout;

public class CustomListViewActivity extends ListView implements View.OnTouchListener, GestureDetector.OnGestureListener {

private final GestureDetector mGestureDetector;
private View mDeletBtn;
private ViewGroup mItemLAyout;
private int mSelecteditem,mlastSelecteditem;
private boolean isDelectShown;
private OnDeleteListener mOnDeleteListener;

public interface OnDeleteListener {
void onDelete(int index);
}

public CustomListViewActivity(Context context, AttributeSet attrs) {
super(context, attrs);
mGestureDetector = new GestureDetector(getContext(), this);
setOnTouchListener(this);
}

public void setOnDeleteListener(OnDeleteListener listener) {
mOnDeleteListener = listener;
}

@Override
public boolean onTouch(View v, MotionEvent event) {
if (isDelectShown) {
Log.d("haha", "onTouch:---isDelectShown ");
hideDelete();
return false;
} else {
return mGestureDetector.onTouchEvent(event);
}
}

@Override
public boolean onDown(MotionEvent e) {
if(!isDelectShown){
mSelecteditem = pointToPosition((int) e.getX(),(int) e.getY());
mlastSelecteditem = mSelecteditem;
Log.d("haha", "onDown: --->mSelecteditem:"+mSelecteditem);
}

return false;
}

@Override
public void onShowPress(MotionEvent e) {
Log.d("haha", "onShowPress: ");
}

@Override
public boolean onSingleTapUp(MotionEvent e) {
Log.d("haha", "onSingleTapUp: ");
return false;
}

@Override
public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX, float distanceY) {
//  Log.d("haha", "onScroll: ");
return false;
}

@Override
public void onLongPress(MotionEvent e) {
Log.d("haha", "onLongPress: ");
}

@Override
public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY) {
mSelecteditem = pointToPosition((int) e2.getX(),(int) e2.getY());
Log.d("haha", "onFling: --->mSelecteditem:"+mSelecteditem);
if(mlastSelecteditem != mSelecteditem && isDelectShown){
hideDelete();
}

if (!isDelectShown && Math.abs(velocityX) > Math.abs(velocityY)) {
mDeletBtn = LayoutInflater.from(getContext()).inflate(R.layout.delect_btn, null);

mDeletBtn.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
mItemLAyout.removeView(mDeletBtn);
mDeletBtn = null;
isDelectShown = false;
Log.d("haha", "onClick:--> delete"+mSelecteditem);
mOnDeleteListener.onDelete(mSelecteditem);
}
});

mItemLAyout = (ViewGroup) getChildAt(mSelecteditem - getFirstVisiblePosition());

RelativeLayout.LayoutParams params = new RelativeLayout.LayoutParams(
LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT);
params.addRule(RelativeLayout.ALIGN_PARENT_RIGHT);
params.addRule(RelativeLayout.CENTER_VERTICAL);

mItemLAyout.addView(mDeletBtn, params);
isDelectShown = true;
}
return false;
}
void hideDelete(){
mItemLAyout.removeView(mDeletBtn);
mDeletBtn = null;
isDelectShown = false;

}

public boolean isDelectShown() {
return isDelectShown;
}
}

3、定义列表项布局custom_listview_item.xml，它的结构很简单，只包含了一个TextView：

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:descendantFocusability="blocksDescendants" >

    <TextView
        android:id="@+id/content_tv"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerVertical="true"
        android:layout_margin="30dp"
        android:gravity="center_vertical|left" />

</RelativeLayout>
</LinearLayout>

4、定义适配器类CustomListViewAdapter，继承自ArrayAdapter<String>：

public class CustomListViewAdapter extends ArrayAdapter<String> {

public CustomListViewAdapter(Context context, int textViewResourceId,
List<String> objects) {
super(context, textViewResourceId, objects);
}

@Override
public View getView(int position, View convertView, ViewGroup parent) {
View view;

if (convertView == null) {
view = LayoutInflater.from(getContext()).inflate(
R.layout.custom_listview_item, null);
} else {
view = convertView;
}

TextView contentTv = (TextView) view.findViewById(R.id.content_tv);
contentTv.setText(getItem(position));

return view;
}

}

5、在activity_main.xml中引入自定义的ListView：

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/main_layout"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical" >

<com.example.test.CustomListView
android:id="@+id/custom_lv"
android:layout_width="match_parent"
android:layout_height="wrap_content" />

6、在MainActivity中对列表做初始化、设置列表项删除按钮点击事件等处理

public class MainActivity extends Activity {

// 自定义Lv
private CustomListView mCustomLv;
// 自定义适配器
private CustomListViewAdapter mAdapter;
// 内容列表
private List<String> contentList = new ArrayList<String>();

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
requestWindowFeature(Window.FEATURE_NO_TITLE);
setContentView(R.layout.activity_main);

initContentList();

mCustomLv = (CustomListView) findViewById(R.id.custom_lv);
mCustomLv.setOnDeleteListener(new OnDeleteListener() {

@Override
public void onDelete(int index) {
contentList.remove(index);
mAdapter.notifyDataSetChanged();
}
});

mAdapter = new CustomListViewAdapter(this, 0, contentList);
mCustomLv.setAdapter(mAdapter);
}

// 初始化内容列表
private void initContentList() {
for (int i = 0; i < 20; i++) {
contentList.add("内容项" + i);
}
}

@Override
public void onBackPressed() {
if (mCustomLv.isDeleteShown()) {
mCustomLv.hideDelete();
return;
}
super.onBackPressed();
}

}

以上代码实现le，自定义View。重点：在重写ListView 时，在类中进行复杂操作。比如点击事件，触摸事件，显示布局，更新布局。在此进行相关的操作～（布局的变化）然后可以写一些接口，可供使用的类调用！