android高效编程之使用本地变量

iteye_21263

于 2010-12-05 14:26:15 发布

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分类专栏： android 开发文章标签：编程 Android C C++ C#

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本文介绍了一种在Android开发中优化代码访问效率的方法：通过将类成员变量赋值给局部变量来减少对成员变量的访问次数，从而提高程序运行效率。这种方法在Dalvik虚拟机上尤为有效。

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hava a look at the following code you will find that

We assign the mNotesCursor field to a local variable at the start of the method. This is done as an optimization of the Android code. Accessing a local variable is much more efficient than accessing a field in the Dalvik VM, so by doing this we make only one access to the field, and five accesses to the local variable, making the routine much more efficient. It is recommended that you use this optimization when possible

   @Override
    protected void onListItemClick(ListView l, View v, int position, long id) {
        super.onListItemClick(l, v, position, id);

        Cursor c = mNotesCursor;//We assign the mNotesCursor field to a local variable
        c.moveToPosition(position);
        Intent i = new Intent(this,NoteEdit.class);
        i.putExtra(NotesDbAdapter.KEY_ROWID, id);
        i.putExtra(NotesDbAdapter.KEY_TITLE,
                c.getString(c.getColumnIndex(NotesDbAdapter.KEY_TITLE)));
        i.putExtra(NotesDbAdapter.KEY_BODY,
                c.getString(c.getColumnIndex(NotesDbAdapter.KEY_BODY)));
        startActivityForResult(i, ACTIVITY_EDIT);

    }