ListView 适配器的优化分析

以通讯卫士黑名单为例进行分析：

1.当适配器作如下配置的时候：

private class CallSmsSafeAdapter extends BaseAdapter {

    @Override

    public int getCount() {

	return infos.size();

    }

    @Override

    public View getView(final int position, View convertView,ViewGroup parent) {

	Log.i(TAG, "创建新的View对象" + position);

	View view = View.inflate(getApplicationContext(),R.layout.list_callsmssafe_item, null);

	TextView tv_number = (TextView) view.findViewById(R.id.tv_number);

	TextView tv_mode = (TextView) view.findViewById(R.id.tv_mode);

	ImageView iv_delete = (ImageView) view.findViewById(R.id.iv_delete);

	String number = infos.get(position).getNumber();

	tv_number.setText(number);

	String mode = infos.get(position).getMode();

	if ("1".equals(mode)) {

	} else if ("2".equals(mode)) {

	    tv_mode.setText("短信拦截");

	} else if ("3".equals(mode)) {

	    tv_mode.setText("电话+短信拦截");

	}

	return view;

    }

    @Override

    public Object getItem(int position) {

	return null;

    }

    @Override

    public long getItemId(int position) {

	return 0;

    }

}

2.每次都新创建一个ListView对象，产生大量的内存垃圾，很快就产生OutOfMemoryError,因此要对内存缓存加以复用！

代码做如下调整：

private class CallSmsSafeAdapter extends BaseAdapter {

    private TextView tv_number;

    private TextView tv_mode;

    private ImageView iv_delete;

    @Override

    public int getCount() {

	return infos.size();

    }

    @Override

    public View getView(final int position, View convertView,ViewGroup parent) {

	View view;

	// 为了减少view对象创建的个数，使用历史缓存

	// convertView instanceof RelativeLayout,这里都是同种缓存可以不写

	if(convertView!=null && convertView instanceof RelativeLayout) {

	    Log.i(TAG, "使用历史缓存的View对象" + position);

	    view = convertView;

	} else {

	    Log.i(TAG, "创建新的View对象" + position);

	    view = View.inflate(getApplicationContext(),R.layout.list_callsmssafe_item, null);

	    tv_number = (TextView) view.findViewById(R.id.tv_number);

	    tv_mode = (TextView) view.findViewById(R.id.tv_mode);

	    iv_delete = (ImageView) view.findViewById(R.id.iv_delete);

	}

	String number = infos.get(position).getNumber();

	tv_number.setText(number);

	String mode = infos.get(position).getMode();

	if ("1".equals(mode)) {

	} else if ("2".equals(mode)) {

    	    tv_mode.setText("短信拦截");

	} else if ("3".equals(mode)) {

	    tv_mode.setText("电话+短信拦截");

	}

	    return view;

    }

    @Override

    public Object getItem(int position) {

	return null;

    }

    @Override

    public long getItemId(int position) {

	return 0;

    }

}

3.使用历史缓存后优化性能已经很高，但是每次还是要执行如下查询的代码，还有进一步优化的空间。

tv_number = (TextView) view.findViewById(R.id.tv_number);

tv_mode = (TextView) view.findViewById(R.id.tv_mode);

iv_delete = (ImageView) view.findViewById(R.id.iv_delete);

查询一次后将其信息保存，以后再查询就不必遍历所有控件。

优化如下：

private class CallSmsSafeAdapter extends BaseAdapter {

    private TextView tv_number;

    private TextView tv_mode;

    private ImageView iv_delete;

    @Override

    public int getCount() {

	return infos.size();

    }

    @Override

    public View getView(final int position, View convertView,ViewGroup parent) {

	View view;

	ViewHolder holder;

	// 为了减少view对象创建的个数，使用历史缓存

	// convertView instanceof RelativeLayout,这里都是同种缓存可以不写

	if(convertView!=null && convertView instanceof RelativeLayout) {

       	    Log.i(TAG, "使用历史缓存的View对象" + position);

	    view = convertView;

       	    holder = (ViewHolder) view.getTag();//取出记事本查找

	} else {

	    Log.i(TAG, "创建新的View对象" + position);

	    holder = new ViewHolder();// 买了一个笔记本，记录孩子信息

            view = View.inflate(getApplicationContext(),R.layout.list_callsmssafe_item, null);

	    holder.tv_number = (TextView) view.findViewById(R.id.tv_number);

	    holder.tv_mode = (TextView) view.findViewById(R.id.tv_mode);

	    holder.iv_delete = (ImageView) view.findViewById(R.id.iv_delete);

	    view.setTag(holder);// 把记事本放在口袋

	}

	String number = infos.get(position).getNumber();

	holder.tv_number.setText(number);

	String mode = infos.get(position).getMode();

	if ("1".equals(mode)) {

	} else if ("2".equals(mode)) {

  	    holder.tv_mode.setText("短信拦截");

	} else if ("3".equals(mode)) {

	    holder.tv_mode.setText("电话+短信拦截");

	}

	return view;

    }

    @Override

    public Object getItem(int position) {

	return null;

    }

    @Override

    public long getItemId(int position) {

        return 0;

    }

}

private class ViewHolder {

    private TextView tv_number;

    private TextView tv_mode;

    private ImageView iv_delete;

}

至此， ListView适配器优化完成。

转载于:https://www.cnblogs.com/loveandroid/p/3802663.html