按钮图像更改的Java代码,按钮图像更改的Java代码
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,
WindowManager.LayoutParams.FLAG_FULLSCREEN);
Button btn=(Button)findViewById(R.id.level1);
btn.setBackgroundColor(Color.BLUE);
// setContentView(new Gameview(this)`enter code here`);
setContentView(R.layout.levels);
addListenerOnButton();
}
存在按钮布局,按钮布局存在
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="@drawable/levelbackground"
android:gravity="center_vertical"
android:orientation="horizontal" >
<TableLayout
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_weight="1.10" >
<TableRow
android:id="@+id/tableRow1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:gravity="center_horizontal" >
<Button
android:id="@+id/level1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginRight="10dp"
android:layout_marginTop="10dp"
android:background="@drawable/level1"
android:height="79dp"
android:width="80dp" />
<Button
android:id="@+id/level2"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginRight="10dp"
android:layout_marginTop="10dp"
android:background="@drawable/levelloked"
android:height="79dp"
android:width="80dp" />
</TableRow>
<TableRow
android:id="@+id/tableRow2"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:gravity="center_horizontal" >
<Button
android:id="@+id/level3"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginRight="10dp"
android:layout_marginTop="10dp"
android:background="@drawable/levelloked"
android:height="79dp"
android:width="80dp" />
<Button
android:id="@+id/level4"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginRight="10dp"
android:layout_marginTop="10dp"
android:background="@drawable/levelloked"
android:height="79dp"
android:width="80dp" />
</TableRow>
<TableRow
android:id="@+id/tableRow3"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:gravity="center_horizontal" >
<Button
android:id="@+id/level5"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginRight="10dp"
android:layout_marginTop="10dp"
android:background="@drawable/levelloked"
android:height="79dp"
android:width="80dp" />
<Button
android:id="@+id/level6"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginRight="10dp"
android:layout_marginTop="10dp"
android:background="@drawable/levelloked"
android:height="79dp"
android:width="80dp" />
</TableRow>
<TableRow
android:id="@+id/tableRow4"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:gravity="center_horizontal" >
</TableRow>
</TableLayout>F
</LinearLayout>
请帮助这个不起作用?我想在代码中更改按钮背景图像?我得到零点异常...
错误记录,错误记录,错误记录
04-19 08:28:43.279: I/ApplicationPackageManager(3716): cscCountry is not German : XSG
04-19 08:28:43.279: D/AndroidRuntime(3716): Shutting down VM
04-19 08:28:43.279: W/dalvikvm(3716): threadid=1: thread exiting with uncaught exception (group=0x40018578)
04-19 08:28:43.289: E/AndroidRuntime(3716): FATAL EXCEPTION: main
04-19 08:28:43.289: E/AndroidRuntime(3716): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.hunter99x/com.hunter99x.LevelsScreen}: java.lang.NullPointerException
04-19 08:28:43.289: E/AndroidRuntime(3716): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1651)
04-19 08:28:43.289: E/AndroidRuntime(3716): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1667)
04-19 08:28:43.289: E/AndroidRuntime(3716): at android.app.ActivityThread.access$1500(ActivityThread.java:117)
04-19 08:28:43.289: E/AndroidRuntime(3716): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:935)
04-19 08:28:43.289: E/AndroidRuntime(3716): at android.os.Handler.dispatchMessage(Handler.java:99)
04-19 08:28:43.289: E/AndroidRuntime(3716): at android.os.Looper.loop(Looper.java:123)
04-19 08:28:43.289: E/AndroidRuntime(3716): at android.app.ActivityThread.main(ActivityThread.java:3687)
04-19 08:28:43.289: E/AndroidRuntime(3716): at java.lang.reflect.Method.invokeNative(Native Method)
04-19 08:28:43.289: E/AndroidRuntime(3716): at java.lang.reflect.Method.invoke(Method.java:507)
04-19 08:28:43.289: E/AndroidRuntime(3716): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:867)
04-19 08:28:43.289: E/AndroidRuntime(3716): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:625)
04-19 08:28:43.289: E/AndroidRuntime(3716): at dalvik.system.NativeStart.main(Native Method)
04-19 08:28:43.289: E/AndroidRuntime(3716): Caused by: java.lang.NullPointerException
04-19 08:28:43.289: E/AndroidRuntime(3716): at com.hunter99x.LevelsScreen.onCreate(LevelsScreen.java:21)
04-19 08:28:43.289: E/AndroidRuntime(3716): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
04-19 08:28:43.289: E/AndroidRuntime(3716): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1615)
04-19 08:28:43.289: E/AndroidRuntime(3716): ... 11 more
答案 0 :(得分:1)
首先加载xml文件,然后挂载所有其他组件。
setContentView(R.layout.levels);
Button btn=(Button)findViewById(R.id.level1);
btn.setBackgroundColor(Color.BLUE);
答案 1 :(得分:1)
在设置布局之前,不能使用任何布局元素。所以使用下面的代码
setContentView(R.layout.levels);
Button btn=(Button)findViewById(R.id.level1);
btn.setBackgroundColor(Color.BLUE);
答案 2 :(得分:0)
Button btn=(Button)findViewById(R.id.level1);
btn.setBackgroundColor(Color.BLUE);
粘贴以下两行
setContentView(R.layout.levels);
我们需要先设置内容视图然后再执行初始化任务。