Android新手入门教程（五）：理解Activityの不得不说的Context

在开发Android的过程中，总是能遇见Context类或者它的实例。Context类的实例经常被用来提供“应用程序”的引用。例如下面的代码片段，Toast类的第一个参数接受一个Context对象：

[java]
@Override
    protected Dialog onCreateDialog(int id) {
        switch (id) {
        case 0:

            Builder builder = new AlertDialog.Builder(this);
            builder.setIcon(R.drawable.ic_launcher);
            builder.setTitle("This is a dialog with some 易做图 text...");
            builder.setPositiveButton("OK",
                    new DialogInte易做图ce.OnClickListener() {
                        public void onClick(DialogInte易做图ce dialog,
                                int whichButton) {
                            Toast.makeText(getBaseContext(), "OK clicked!",
                                    Toast.LENGTH_SHORT).show();
                        }
                    });

            builder.setNegativeButton("Cancel",
                    new DialogInte易做图ce.OnClickListener() {
                        public void onClick(DialogInte易做图ce dialog,
                                int whichButton) {
                            Toast.makeText(getBaseContext(), "Cancel clicked!",
                                    Toast.LENGTH_SHORT).show();
                        }
                    });

            builder.setMultiChoiceItems(items, itemsChecked,
                    new DialogInte易做图ce.OnMultiChoiceClickListener() {
                        public void onClick(DialogInte易做图ce dialog, int which,
                                boolean isChecked) {
                            Toast.makeText(
                                    getBaseContext(),
                                    items[which]
                                            + (isChecked ? " checked!"
                                                    : " unchecked!"),
                                    Toast.LENGTH_SHORT).show();
                        }
                    });
            return builder.create();

        }
        return null;
    }
@Override
    protected Dialog onCreateDialog(int id) {
        switch (id) {
        case 0:

            Builder builder = new AlertDialog.Builder(this);
            builder.setIcon(R.drawable.ic_launcher);
            builder.setTitle("This is a dialog with some 易做图 text...");
            builder.setPositiveButton("OK",
                    new DialogInte易做图ce.OnClickListener() {
                        public void onClick(DialogInte易做图ce dialog,
                                int whichButton) {
        &nb

补充：移动开发 , Android ,