以下是我想要完成的。劃分垂直和水平線/視圖
綠線是一條垂直線,這將是一個簡單的查看。紅線將是一條水平線,也是一個簡單的視圖。我想要從RelativeLayout頂部的紅線X量的DPS /像素。然後我想讓綠線水平居中,然後從RelativeLayout頂部延伸到「紅線上方」。
以下是我編譯的代碼,但會產生運行時錯誤。
public class Puzzle extends Activity {
RelativeLayout relativelayout;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
relativelayout = new RelativeLayout(getApplicationContext());
dividers();
setContentView(relativelayout);
}
public void dividers() {
// horizontal line
View view0 = new View(this);
view0.setBackgroundColor(0xFFC2BEBF);
relativelayout.addView(view0, new ViewGroup.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT, 2));
view0.setId(0);
RelativeLayout.LayoutParams params0 = null;
params0.addRule(RelativeLayout.CENTER_VERTICAL); // line 39
view0.setLayoutParams(params0);
// vertical line
View view1 = new View(this);
view1.setBackgroundColor(0xFFC2BEBF);
relativelayout.addView(view1, new ViewGroup.LayoutParams(2, ViewGroup.LayoutParams.MATCH_PARENT));
RelativeLayout.LayoutParams params1 = null;
params1.addRule(RelativeLayout.CENTER_HORIZONTAL);
params1.addRule(RelativeLayout.ABOVE, view0.getId());
view1.setLayoutParams(params1);
}
}
以下是LogCat輸出。
11-22 00:25:02.500: E/AndroidRuntime(4140): FATAL EXCEPTION: main
11-22 00:25:02.500: E/AndroidRuntime(4140): Process: matt.lyons.tileslider, PID: 4140
11-22 00:25:02.500: E/AndroidRuntime(4140): java.lang.RuntimeException: Unable to start activity ComponentInfo{matt.lyons.tileslider/matt.lyons.tileslider.Puzzle}: java.lang.NullPointerException
11-22 00:25:02.500: E/AndroidRuntime(4140): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2176)
11-22 00:25:02.500: E/AndroidRuntime(4140): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2226)
11-22 00:25:02.500: E/AndroidRuntime(4140): at android.app.ActivityThread.access$700(ActivityThread.java:135)
11-22 00:25:02.500: E/AndroidRuntime(4140): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1397)
11-22 00:25:02.500: E/AndroidRuntime(4140): at android.os.Handler.dispatchMessage(Handler.java:102)
11-22 00:25:02.500: E/AndroidRuntime(4140): at android.os.Looper.loop(Looper.java:137)
11-22 00:25:02.500: E/AndroidRuntime(4140): at android.app.ActivityThread.main(ActivityThread.java:4998)
11-22 00:25:02.500: E/AndroidRuntime(4140): at java.lang.reflect.Method.invokeNative(Native Method)
11-22 00:25:02.500: E/AndroidRuntime(4140): at java.lang.reflect.Method.invoke(Method.java:515)
11-22 00:25:02.500: E/AndroidRuntime(4140): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:777)
11-22 00:25:02.500: E/AndroidRuntime(4140): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:593)
11-22 00:25:02.500: E/AndroidRuntime(4140): at dalvik.system.NativeStart.main(Native Method)
11-22 00:25:02.500: E/AndroidRuntime(4140): Caused by: java.lang.NullPointerException
11-22 00:25:02.500: E/AndroidRuntime(4140): at matt.lyons.tileslider.Puzzle.dividers(Puzzle.java:39)
11-22 00:25:02.500: E/AndroidRuntime(4140): at matt.lyons.tileslider.Puzzle.onCreate(Puzzle.java:24)
11-22 00:25:02.500: E/AndroidRuntime(4140): at android.app.Activity.performCreate(Activity.java:5243)
11-22 00:25:02.500: E/AndroidRuntime(4140): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
11-22 00:25:02.500: E/AndroidRuntime(4140): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2140)
11-22 00:25:02.500: E/AndroidRuntime(4140): ... 11 more
我已經註釋了我的代碼,其中第39行是。我是新手,在沒有XML的情況下用Java完成整個佈局,所以我有點困惑於如何做到這一點,所以任何幫助表示讚賞。我爲什麼得到這個NPE?
'RelativeLayout.LayoutParams params0 = null;'你很驚訝在下一行有NPE嗎? – njzk2
嗯,我不想爲高度和寬度輸入2個數字,因爲我聲明瞭這個視圖的大小,像這樣:'relativelayout.addView(view0,new ViewGroup.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT ,2));'。我想我只是不知道如何設置「params0」等於。 – Matt
有關新的'RelativeLayout.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT,2)'的說法,因爲你之前已經使用過這兩行了? – njzk2