Android ListView内部组件事件响应

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Android ListView内部组件事件响应
最近项目需要实现一个下载模块，界面布局就采用常见的ListView方式，实现的界面效果：

可是在事件监听的过程中出现问题了，内部组件如Button无法捕获到点击事件OnClick ：这个问题还好解决，通过给Button设定
Xml代码
android:focusable="false"
```
android:focusable="false"
```
然后给ListView的item布局文件的最顶层组件添加：
Xml代码
android:descendantFocusability="blocksDescendants"
```
android:descendantFocusability="blocksDescendants"
```
这样就可以同时相应Button的点击事件和Item的点击事件了。

但是，在点击后面的下载按钮时，会出现同时有两个按钮状态发生变化，ListView的Adapter的代码如下：
Java代码
private class DownloadListAdapter extends BaseAdapter{
        private Context mContext;
        private LayoutInflater inflater;
        private List<Download> data;
        private int resource;

        public DownloadListAdapter(Context context,
                List<Download> data, int resource) {
            super();
            mContext = context;
            inflater = (LayoutInflater)context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
            this.data = data;
            this.resource = resource;
        }

        @Override
        public int getCount() {
            return data.size();
        }

        @Override
        public Object getItem(int position) {
            if(position < data.size()){
                return data.get(position);
            }
            return null;
        }

        @Override
        public long getItemId(int position) {
            return position;
        }

        @Override
        public View getView(int position, View convertView, ViewGroup parent){
            final Download down = (Download)getItem(position);
            if(convertView == null){
                convertView = inflater.inflate(resource, parent,false);

                ImageButton btn = (ImageButton)convertView.findViewById(R.id.down_pause);
                //添加事件监听
                btn.setOnClickListener(new OnClickListener() {
                    @Override
                    public void onClick(View v) {
                        Log.d(TAG,"添加事件监听："+ v.hashCode() +" - "+down.getId());
                        if(down.getStatus() == Downloader.STATUS_RUNNING){
                            Log.d(TAG, "暂停下载 : "+down.getId());
                            mDownloader.pause(down.getId());
                            down.setStatus(Downloader.STATUS_PAUSED);
                        }else if(down.getStatus() == Downloader.STATUS_PAUSED){
                            Log.d(TAG, "继续下载 : "+down.getId());
                            mDownloader.continueDownload(down.getId());
                            down.setStatus(Downloader.STATUS_RUNNING);
                        }
                        //DownloadListAdapter.this.notifyDataSetChanged();
                        return ;
                    }
                });
            }
            TextView nameText = (TextView)convertView.findViewById(R.id.down_name);
            ProgressBar bar = (ProgressBar)convertView.findViewById(R.id.down_progress);
            ImageButton btn = (ImageButton)convertView.findViewById(R.id.down_pause);

            int progress = (int)(down.getDownloadSize()*100/down.getSize());
            String name = down.getName();

            nameText.setText(name);
            bar.setProgress(progress);
            Log.d(TAG, "状态："+down.getStatus());

            return convertView;
        }
```
private class DownloadListAdapter extends BaseAdapter{
		private Context mContext;
		private LayoutInflater inflater;
		private List<Download> data;
		private int resource;
		
		public DownloadListAdapter(Context context,
				List<Download> data, int resource) {
			super();
			mContext = context;
			inflater = (LayoutInflater)context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
			this.data = data;
			this.resource = resource;
		}
		
		@Override
		public int getCount() {
			return data.size();
		}
		
		@Override
		public Object getItem(int position) {
			if(position < data.size()){
				return data.get(position);
			}
			return null;
		}
		
		@Override
		public long getItemId(int position) {
			return position;
		}
		
		@Override
		public View getView(int position, View convertView, ViewGroup parent){
			final Download down = (Download)getItem(position);
			if(convertView == null){
				convertView = inflater.inflate(resource, parent,false);
				
				ImageButton btn = (ImageButton)convertView.findViewById(R.id.down_pause);
				//添加事件监听
				btn.setOnClickListener(new OnClickListener() {
					@Override
					public void onClick(View v) {
						Log.d(TAG,"添加事件监听："+ v.hashCode() +" - "+down.getId());
						if(down.getStatus() == Downloader.STATUS_RUNNING){
							Log.d(TAG, "暂停下载 : "+down.getId());
							mDownloader.pause(down.getId());
							down.setStatus(Downloader.STATUS_PAUSED);
						}else if(down.getStatus() == Downloader.STATUS_PAUSED){
							Log.d(TAG, "继续下载 : "+down.getId());
							mDownloader.continueDownload(down.getId());
							down.setStatus(Downloader.STATUS_RUNNING);
						}
						//DownloadListAdapter.this.notifyDataSetChanged();
						return ;
					}
				});
			}
			TextView nameText = (TextView)convertView.findViewById(R.id.down_name);
			ProgressBar bar = (ProgressBar)convertView.findViewById(R.id.down_progress);
			ImageButton btn = (ImageButton)convertView.findViewById(R.id.down_pause);
			
			int progress = (int)(down.getDownloadSize()*100/down.getSize());
			String name = down.getName();
			
			nameText.setText(name);
			bar.setProgress(progress);
			Log.d(TAG, "状态："+down.getStatus());
			
			return convertView;
		}
```
事件监听器是在每个Item第一次初始化的时候添加的，而且也只添加了一次，同时日志跟踪，在点击最后一个按钮的时候，OnClick里面的日志也显示只调用了一次，但是界面的上的第一个按钮的状态也跟着发生变化。

纠结了很久都没弄清楚到底是哪里的问题。分析可能的原因：ImageButton btn =(ImageButton)convertView.findViewById(R.id.down_pause);是通过这种方式获得，而ListView里面所有的Item都共用一个布局文件，也就是上面的所有的convertView都是通过一个布局文件构造出来的，感觉这里会发生问题，但是貌似又没问题，在添加事件监听的过程中，打印的对应组件的hashCode又是不一样的，也就是每个按钮的事件监听器都是不一样的，这样分析之后又困惑了！

最后改用下面的方式解决问题了，关键部分代码如下：
Java代码
@Override
        public View getView(int position, View convertView, ViewGroup parent){
            final Download down = (Download)getItem(position);
            Holder holder = null;
            if(convertView == null){
                convertView = inflater.inflate(resource, parent,false);

                holder = new Holder();
                holder.text = (TextView)convertView.findViewById(R.id.down_name);
                holder.bar = (ProgressBar)convertView.findViewById(R.id.down_progress);
                holder.imageBtn = (ImageButton)convertView.findViewById(R.id.down_pause);

                convertView.setTag(holder);

                //添加事件监听
                holder.imageBtn.setOnClickListener(new OnClickListener() {
                    @Override
                    public void onClick(View v) {
                        Log.d(TAG,"添加事件监听："+ v.hashCode() +" - "+down.getId());
                        if(down.getStatus() == Downloader.STATUS_RUNNING){
                            Log.d(TAG, "暂停下载 : "+down.getId());
                            mDownloader.pause(down.getId());
                            down.setStatus(Downloader.STATUS_PAUSED);
                        }else if(down.getStatus() == Downloader.STATUS_PAUSED){
                            Log.d(TAG, "继续下载 : "+down.getId());
                            mDownloader.continueDownload(down.getId());
                            down.setStatus(Downloader.STATUS_RUNNING);
                        }
                        //DownloadListAdapter.this.notifyDataSetChanged();
                        return ;
                    }
                });
            }else{
                holder = (Holder)convertView.getTag();
            }

            int progress = (int)(down.getDownloadSize()*100/down.getSize());
            String name = down.getName();

            holder.text.setText(name);
            holder.bar.setProgress(progress);
            Log.d(TAG, "状态："+down.getStatus());


            return convertView;
        }
```
@Override
		public View getView(int position, View convertView, ViewGroup parent){
			final Download down = (Download)getItem(position);
			Holder holder = null;
			if(convertView == null){
				convertView = inflater.inflate(resource, parent,false);
				
				holder = new Holder();
				holder.text = (TextView)convertView.findViewById(R.id.down_name);
				holder.bar = (ProgressBar)convertView.findViewById(R.id.down_progress);
				holder.imageBtn = (ImageButton)convertView.findViewById(R.id.down_pause);
				
				convertView.setTag(holder);
				
				//添加事件监听
				holder.imageBtn.setOnClickListener(new OnClickListener() {
					@Override
					public void onClick(View v) {
						Log.d(TAG,"添加事件监听："+ v.hashCode() +" - "+down.getId());
						if(down.getStatus() == Downloader.STATUS_RUNNING){
							Log.d(TAG, "暂停下载 : "+down.getId());
							mDownloader.pause(down.getId());
							down.setStatus(Downloader.STATUS_PAUSED);
						}else if(down.getStatus() == Downloader.STATUS_PAUSED){
							Log.d(TAG, "继续下载 : "+down.getId());
							mDownloader.continueDownload(down.getId());
							down.setStatus(Downloader.STATUS_RUNNING);
						}
						//DownloadListAdapter.this.notifyDataSetChanged();
						return ;
					}
				});
			}else{
				holder = (Holder)convertView.getTag();
			}
			
			int progress = (int)(down.getDownloadSize()*100/down.getSize());
			String name = down.getName();
			
			holder.text.setText(name);
			holder.bar.setProgress(progress);
			Log.d(TAG, "状态："+down.getStatus());

			
			return convertView;
		}
```
Holder定义如下：
Java代码
class Holder {
            public TextView text;
            public ImageButton imageBtn;
            public ProgressBar bar;
        }
```
class Holder {
			public TextView text;
			public ImageButton imageBtn;
			public ProgressBar bar;
		}
```
分析上面的代码，感觉没大的区别，虽然问题解决了，但是没搞懂为什么？

悲剧，在新插入item以后，问题又出现了！
转自：http://aswang.iteye.com/blog/1490245
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原文地址：https://www.cnblogs.com/bmate/p/2674003.html