代码实现Selector按钮点击效果

用途：动态设置Button、ImageView等组件在不同状态下的背景/前景显示效果。
扩展下的话可以前景/背景的显示效果可以使用网络图片。
优点：灵活，减少xml的编写。

参考：
[AndroidOpenSource]frameworksasecorejavaandroidviewview.xml
[AndroidOpenSource]frameworksasecore
es
esvaluespublic.xml
代码如下：

/** 设置Selector。 */

public static StateListDrawable newSelector(Context context, int idNormal, int idPressed, int idFocused,

int idUnable) {

StateListDrawable bg = new StateListDrawable();

Drawable normal = idNormal == -1 ? null : context.getResources().getDrawable(idNormal);

Drawable pressed = idPressed == -1 ? null : context.getResources().getDrawable(idPressed);

Drawable focused = idFocused == -1 ? null : context.getResources().getDrawable(idFocused);

Drawable unable = idUnable == -1 ? null : context.getResources().getDrawable(idUnable);

// View.PRESSED_ENABLED_STATE_SET

bg.addState(new int[] { android.R.attr.state_pressed, android.R.attr.state_enabled }, pressed);

// View.ENABLED_FOCUSED_STATE_SET

bg.addState(new int[] { android.R.attr.state_enabled, android.R.attr.state_focused }, focused);

// View.ENABLED_STATE_SET

bg.addState(new int[] { android.R.attr.state_enabled }, normal);

// View.FOCUSED_STATE_SET

bg.addState(new int[] { android.R.attr.state_focused }, focused);

// View.WINDOW_FOCUSED_STATE_SET

bg.addState(new int[] { android.R.attr.state_window_focused }, unable);

// View.EMPTY_STATE_SET

bg.addState(new int[] {}, normal);

return bg;

}

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示例代码：

Button btnNormal = (Button) findViewById(R.id.btnSampleNormal);

btnNormal.setBackgroundDrawable(newSelector(this, R.drawable.btn_normal, R.drawable.btn_selected,

R.drawable.btn_selected, R.drawable.btn_unable));

Button btnUnable = (Button) findViewById(R.id.btnSampleUnable);

btnUnable.setBackgroundDrawable(newSelector(this, R.drawable.btn_normal, R.drawable.btn_selected,

R.drawable.btn_selected, R.drawable.btn_unable));

btnUnable.setEnabled(false);

btnUnable.setOnClickListener(this);

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/** 对TextView设置不同状态时其文字颜色。 */

private ColorStateList createColorStateList(int normal, int pressed, int focused, int unable) {

int[] colors = new int[] { pressed, focused, normal, focused, unable, normal };

int[][] states = new int[6][];

states[0] = new int[] { android.R.attr.state_pressed, android.R.attr.state_enabled };

states[1] = new int[] { android.R.attr.state_enabled, android.R.attr.state_focused };

states[2] = new int[] { android.R.attr.state_enabled };

states[3] = new int[] { android.R.attr.state_focused };

states[4] = new int[] { android.R.attr.state_window_focused };

states[5] = new int[] {};

ColorStateList colorList = new ColorStateList(states, colors);

return colorList;

}