-2
我的應用程序有2個活動：按鈕背景是否自動更改？
MainActivity有一個按鈕，啓動子活動，該按鈕未設置透明。
SubActivity有一個由setAlpha（）透明的按鈕。
我的問題是有時，當我通過按下後退按鈕返回到MainActivity從子活動，MainActivity的按鈕變爲透明相同子活動的按鈕。如果我退出應用程序並再次打開，則會頻繁發生此問題。
我也嘗試在每個活動的onResume（）中設置按鈕1和按鈕2的alpha 255，但它不起作用。有時button1變得透明，有時button2不透明。
我上傳MainActivity.java：
package com.example.buttondemo;
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.Menu;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
public class MainActivity extends Activity implements OnClickListener {
private Button button1;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
button1 = (Button) findViewById(R.id.button1);
button1.setOnClickListener(this);
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
@Override
public void onClick(View v) {
switch (v.getId()) {
case R.id.button1:
startActivity(new Intent(this, SubActivity.class));
break;
default:
break;
}
}
}
SubActivity.java：
package com.example.buttondemo;
import android.app.Activity;
import android.os.Bundle;
import android.view.Menu;
import android.widget.Button;
public class SubActivity extends Activity {
private Button button2;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_sub);
button2 = (Button) findViewById(R.id.button2);
button2.getBackground().setAlpha(120);
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.sub, menu);
return true;
}
}
\水庫\值\ strings.xml中：
<string name="app_name">ButtonDemo</string>
<string name="action_settings">Settings</string>
<string name="hello_world">Hello world!</string>
<string name="title_activity_sub">SubActivity</string>
<string name="button1_label">button1</string>
<string name="button2_label">button2</string>
\ res \ layout \ activity_main.xml;
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context=".MainActivity" >
<Button
android:id="@+id/button1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/button1_label"
android:background="@drawable/button_selector" />
</RelativeLayout>
\水庫\佈局\ activity_sub.xml：
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context=".SubActivity" >
<Button
android:id="@+id/button2"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/button2_label"
android:background="@drawable/button_selector" />
</RelativeLayout>
\水庫\繪製\ button_selector.xml：
<selector
xmlns:android="http://schemas.android.com/apk/res/android">
<item
android:state_pressed="true"
android:drawable="@drawable/pressed_button" /> <!-- pressed -->
<item
android:state_focused="true"
android:drawable="@drawable/pressed_button" /> <!-- focused -->
<item
android:drawable="@drawable/default_button" /> <!-- default -->
</selector>