Question

我一直致力于创建可变数量的自定义视图，但我无法创建任何不会导致应用程序强制停止的内容。我查看了几个不同的资源，但一直找不到任何帮助。对不起，如果这很明显，我对此有点新鲜。

我的主要活动代码

package com.example.customview;

import android.app.Activity;
import android.os.Bundle;
import android.widget.LinearLayout;
import com.example.customview.widget.DoubleImageView;

public class MainActivity extends Activity {

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        LinearLayout linearlayout = (LinearLayout) findViewById(R.id.linear_layout);
        DoubleImageView doubleimageview;
        for (int i =0; i <5; i++) {
            doubleimageview = new DoubleImageView(this);
            linearlayout.addView(doubleimageview);
        }
    }
}

我的Double_image.xml

<?xml version="1.0" encoding="utf-8"?>
<ScrollView xmlns:android="http://schemas.android.com/apk/res/android"
        android:orientation="vertical"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent">
    <LinearLayout android:id="@+id/linear_layout"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:gravity="center"
        android:orientation="vertical">
            <com.example.customview.widget.DoubleImageView
                android:id="@+id/image1"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:drawableLeft="@drawable/flag_us"
                android:drawableRight="@drawable/flag_uk"
                android:textColor="#FFF"
                android:textSize="32sp"
                android:text="@string/score"
                android:spacing="15dp"/>

    </LinearLayout>
</ScrollView>

对我而言，这应该可以将double_image视图添加到可滚动的线性布局中，我不确定缺少什么。

这是我的错误日志

＆＃13;

11-05 20:43:58.552: E/AndroidRuntime(29844): FATAL EXCEPTION: main
11-05 20:43:58.552: E/AndroidRuntime(29844): Process: com.example.customview, PID: 29844
11-05 20:43:58.552: E/AndroidRuntime(29844): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.customview/com.example.customview.MainActivity}: java.lang.NullPointerException
11-05 20:43:58.552: E/AndroidRuntime(29844): 	at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2200)
11-05 20:43:58.552: E/AndroidRuntime(29844): 	at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2250)
11-05 20:43:58.552: E/AndroidRuntime(29844): 	at android.app.ActivityThread.access$800(ActivityThread.java:139)
11-05 20:43:58.552: E/AndroidRuntime(29844): 	at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1200)
11-05 20:43:58.552: E/AndroidRuntime(29844): 	at android.os.Handler.dispatchMessage(Handler.java:102)
11-05 20:43:58.552: E/AndroidRuntime(29844): 	at android.os.Looper.loop(Looper.java:136)
11-05 20:43:58.552: E/AndroidRuntime(29844): 	at android.app.ActivityThread.main(ActivityThread.java:5105)
11-05 20:43:58.552: E/AndroidRuntime(29844): 	at java.lang.reflect.Method.invokeNative(Native Method)
11-05 20:43:58.552: E/AndroidRuntime(29844): 	at java.lang.reflect.Method.invoke(Method.java:515)
11-05 20:43:58.552: E/AndroidRuntime(29844): 	at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:792)
11-05 20:43:58.552: E/AndroidRuntime(29844): 	at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:608)
11-05 20:43:58.552: E/AndroidRuntime(29844): 	at dalvik.system.NativeStart.main(Native Method)
11-05 20:43:58.552: E/AndroidRuntime(29844): Caused by: java.lang.NullPointerException
11-05 20:43:58.552: E/AndroidRuntime(29844): 	at com.example.customview.MainActivity.onCreate(MainActivity.java:40)
11-05 20:43:58.552: E/AndroidRuntime(29844): 	at android.app.Activity.performCreate(Activity.java:5275)
11-05 20:43:58.552: E/AndroidRuntime(29844): 	at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
11-05 20:43:58.552: E/AndroidRuntime(29844): 	at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2164)
11-05 20:43:58.552: E/AndroidRuntime(29844): 	... 11 more

＆＃13;

Answer 1

您没有在setContentView()中调用onCreate()，这意味着findViewById()肯定会返回null。方法应该是这样的：

protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.double_image);
    LinearLayout linearlayout = (LinearLayout) findViewById(R.id.linear_layout);
    ...

创建可变数量的视图

1 个答案: