在Android中动态实例化按钮

问题描述 投票：0回答：2

假设我在activity_main.xml中有10个按钮，它们的ID为b1，b2，b3，b4 ...到... b10；我想动态实例化它们。我尝试了以下代码。

Button b[] = new Button[10];

@Override
    protected void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        for( int i = 0; i < b.length ; i++ )
        {
            b[i] = (Button)findViewById(getResources().getIdentifier("b"+(i+1), "drawable", getPackageName()));
            System.out.println("TAG OF "+b[i].getId()+" is "+b[i].getTag());
        }
    }

我收到以下错误

2019-09-28 23:18:40.250 3096-3096/? E/Zygote: isWhitelistProcess - Process is Whitelisted
2019-09-28 23:18:40.250 3096-3096/? E/libpersona: scanKnoxPersonas
2019-09-28 23:18:40.250 3096-3096/? E/libpersona: Couldn't open the File - /data/system/users/0/personalist.xml - No such file or directory
2019-09-28 23:18:41.237 3096-3096/com.example.raagidentifier E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.example.raagidentifier, PID: 3096
    java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.raagidentifier/com.example.raagidentifier.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'int android.widget.Button.getId()' on a null object reference
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2974)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3059)
        at android.app.ActivityThread.-wrap11(Unknown Source:0)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1724)
        at android.os.Handler.dispatchMessage(Handler.java:106)
        at android.os.Looper.loop(Looper.java:164)
        at android.app.ActivityThread.main(ActivityThread.java:7000)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:441)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1408)
     Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'int android.widget.Button.getId()' on a null object reference
        at com.example.raagidentifier.MainActivity.onCreate(MainActivity.java:23)
        at android.app.Activity.performCreate(Activity.java:7258)
        at android.app.Activity.performCreate(Activity.java:7249)
        at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1222)
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2927)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3059) 
        at android.app.ActivityThread.-wrap11(Unknown Source:0) 
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1724) 
        at android.os.Handler.dispatchMessage(Handler.java:106) 
        at android.os.Looper.loop(Looper.java:164) 
        at android.app.ActivityThread.main(ActivityThread.java:7000) 
        at java.lang.reflect.Method.invoke(Native Method) 
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:441) 
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1408) 

如何获得理想的结果？

UPDATE

根据评论中的建议，我使用“ id”代替“ drawable”。

b[i] = (Button)findViewById(getResources().getIdentifier("b"+(i+1), "id", getPackageName()));

我收到以下错误。

09/29 00:38:57: Launching 'app' on samsung SM-G610F.
$ adb shell am start -n "com.example.raagidentifier/com.example.raagidentifier.MainActivity" -a android.intent.action.MAIN -c android.intent.category.LAUNCHER
Waiting for process to come online...
Connected to process 10760 on device 'samsung-sm_g610f-52001c95fe0794f1'.
Capturing and displaying logcat messages from application. This behavior can be disabled in the "Logcat output" section of the "Debugger" settings page.
I/zygote: Rejecting re-init on previously-failed class java.lang.Class<androidx.core.view.ViewCompat$2>: java.lang.NoClassDefFoundError: Failed resolution of: Landroid/view/View$OnUnhandledKeyEventListener;
        at void androidx.core.view.ViewCompat.setBackground(android.view.View, android.graphics.drawable.Drawable) (ViewCompat.java:2559)
        at void androidx.appcompat.widget.ActionBarContainer.<init>(android.content.Context, android.util.AttributeSet) (ActionBarContainer.java:63)
        at java.lang.Object java.lang.reflect.Constructor.newInstance0(java.lang.Object[]) (Constructor.java:-2)
        at java.lang.Object java.lang.reflect.Constructor.newInstance(java.lang.Object[]) (Constructor.java:334)
        at android.view.View android.view.LayoutInflater.createView(java.lang.String, java.lang.String, android.util.AttributeSet) (LayoutInflater.java:647)
        at android.view.View android.view.LayoutInflater.createViewFromTag(android.view.View, java.lang.String, android.content.Context, android.util.AttributeSet, boolean) (LayoutInflater.java:790)
        at android.view.View android.view.LayoutInflater.createViewFromTag(android.view.View, java.lang.String, android.content.Context, android.util.AttributeSet) (LayoutInflater.java:730)
        at void android.view.LayoutInflater.rInflate(org.xmlpull.v1.XmlPullParser, android.view.View, android.content.Context, android.util.AttributeSet, boolean) (LayoutInflater.java:863)
        at void android.view.LayoutInflater.rInflateChildren(org.xmlpull.v1.XmlPullParser, android.view.View, android.util.AttributeSet, boolean) (LayoutInflater.java:824)
        at android.view.View android.view.LayoutInflater.inflate(org.xmlpull.v1.XmlPullParser, android.view.ViewGroup, boolean) (LayoutInflater.java:515)
        at android.view.View android.view.LayoutInflater.inflate(int, android.view.ViewGroup, boolean) (LayoutInflater.java:423)
        at android.view.View android.view.LayoutInflater.inflate(int, android.view.ViewGroup) (LayoutInflater.java:374)
        at android.view.ViewGroup androidx.appcompat.app.AppCompatDelegateImpl.createSubDecor() (AppCompatDelegateImpl.java:749)
        at void androidx.appcompat.app.AppCompatDelegateImpl.ensureSubDecor() (AppCompatDelegateImpl.java:659)
        at void androidx.appcompat.app.AppCompatDelegateImpl.setContentView(int) (AppCompatDelegateImpl.java:552)
        at void androidx.appcompat.app.AppCompatActivity.setContentView(int) (AppCompatActivity.java:161)
        at void com.example.raagidentifier.MainActivity.onCreate(android.os.Bundle) (MainActivity.java:18)
        at void android.app.Activity.performCreate(android.os.Bundle, android.os.PersistableBundle) (Activity.java:7258)
        at void android.app.Activity.performCreate(android.os.Bundle) (Activity.java:7249)
        at void android.app.Instrumentation.callActivityOnCreate(android.app.Activity, android.os.Bundle) (Instrumentation.java:1222)
        at android.app.Activity android.app.ActivityThread.performLaunchActivity(android.app.ActivityThread$ActivityClientRecord, android.content.Intent) (ActivityThread.java:2927)
        at void android.app.ActivityThread.handleLaunchActivity(android.app.ActivityThread$ActivityClientRecord, android.content.Intent, java.lang.String) (ActivityThread.java:3059)
        at void android.app.ActivityThread.-wrap11(android.app.ActivityThread, android.app.ActivityThread$ActivityClientRecord, android.content.Intent, java.lang.String) (ActivityThread.java:-1)
        at void android.app.ActivityThread$H.handleMessage(android.os.Message) (ActivityThread.java:1724)
        at void android.os.Handler.dispatchMessage(android.os.Message) (Handler.java:106)
        at void android.os.Looper.loop() (Looper.java:164)
        at void android.app.ActivityThread.main(java.lang.String[]) (ActivityThread.java:7000)
        at java.lang.Object java.lang.reflect.Method.invoke(java.lang.Object, java.lang.Object[]) (Method.java:-2)
        at void com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run() (RuntimeInit.java:441)
        at void com.android.internal.os.ZygoteInit.main(java.lang.String[]) (ZygoteInit.java:1408)
    Caused by: java.lang.ClassNotFoundException: Didn't find class "android.view.View$OnUnhandledKeyEventListener" on path: DexPathList[[zip file "/data/app/com.example.raagidentifier-9TtRSpsKjCr22NxWyAtMAQ==/base.apk"],nativeLibraryDirectories=[/data/app/com.example.raagidentifier-9TtRSpsKjCr22NxWyAtMAQ==/lib/arm, /system/lib, /system/vendor/lib]]
        at java.lang.Class dalvik.system.BaseDexClassLoader.findClass(java.lang.String) (BaseDexClassLoader.java:125)
        at java.lang.Class java.lang.ClassLoader.loadClass(java.lang.String, boolean) (ClassLoader.java:379)
        at java.lang.Class java.lang.ClassLoader.loadClass(java.lang.String) (ClassLoader.java:312)
        at void androidx.core.view.ViewCompat.setBackground(android.view.View, android.graphics.drawable.Drawable) (ViewCompat.java:2559)
        at void androidx.appcompat.widget.ActionBarContainer.<init>(android.content.Context, android.util.AttributeSet) (ActionBarContainer.java:63)
        at java.lang.Object java.lang.reflect.Constructor.newInstance0(java.lang.Object[]) (Constructor.java:-2)
        at java.lang.Object java.lang.reflect.Constructor.newInstance(java.lang.Object[]) (Constructor.java:334)
        at android.view.View android.view.LayoutInflater.createView(java.lang.String, java.lang.String, android.util.AttributeSet) (LayoutInflater.java:647)
        at android.view.View android.view.LayoutInflater.createViewFromTag(android.view.View, java.lang.String, android.content.Context, android.util.AttributeSet, boolean) (LayoutInflater.java:790)
        at android.view.View android.view.LayoutInflater.createViewFromTag(android.view.View, java.lang.String, android.content.Context, android.util.AttributeSet) (LayoutInflater.java:730)
        at void android.view.LayoutInflater.rInflate(org.xmlpull.v1.XmlPullParser, android.view.View, android.content.Context, android.util.AttributeSet, boolean) (LayoutInflater.java:863)
        at void android.view.LayoutInflater.rInflateChildren(org.xmlpull.v1.XmlPullParser, android.view.View, android.util.AttributeSet, boolean) (LayoutInflater.java:824)
        at android.view.View android.view.LayoutInflater.inflate(org.xmlpull.v1.XmlPullParser, android.view.ViewGroup, boolean) (LayoutInflater.java:515)
I/zygote:     at android.view.View android.view.LayoutInflater.inflate(int, android.view.ViewGroup, boolean) (LayoutInflater.java:423)
        at android.view.View android.view.LayoutInflater.inflate(int, android.view.ViewGroup) (LayoutInflater.java:374)
        at android.view.ViewGroup androidx.appcompat.app.AppCompatDelegateImpl.createSubDecor() (AppCompatDelegateImpl.java:749)
        at void androidx.appcompat.app.AppCompatDelegateImpl.ensureSubDecor() (AppCompatDelegateImpl.java:659)
        at void androidx.appcompat.app.AppCompatDelegateImpl.setContentView(int) (AppCompatDelegateImpl.java:552)
        at void androidx.appcompat.app.AppCompatActivity.setContentView(int) (AppCompatActivity.java:161)
        at void com.example.raagidentifier.MainActivity.onCreate(android.os.Bundle) (MainActivity.java:18)
        at void android.app.Activity.performCreate(android.os.Bundle, android.os.PersistableBundle) (Activity.java:7258)
        at void android.app.Activity.performCreate(android.os.Bundle) (Activity.java:7249)
        at void android.app.Instrumentation.callActivityOnCreate(android.app.Activity, android.os.Bundle) (Instrumentation.java:1222)
        at android.app.Activity android.app.ActivityThread.performLaunchActivity(android.app.ActivityThread$ActivityClientRecord, android.content.Intent) (ActivityThread.java:2927)
        at void android.app.ActivityThread.handleLaunchActivity(android.app.ActivityThread$ActivityClientRecord, android.content.Intent, java.lang.String) (ActivityThread.java:3059)
        at void android.app.ActivityThread.-wrap11(android.app.ActivityThread, android.app.ActivityThread$ActivityClientRecord, android.content.Intent, java.lang.String) (ActivityThread.java:-1)
        at void android.app.ActivityThread$H.handleMessage(android.os.Message) (ActivityThread.java:1724)
        at void android.os.Handler.dispatchMessage(android.os.Message) (Handler.java:106)
        at void android.os.Looper.loop() (Looper.java:164)
        at void android.app.ActivityThread.main(java.lang.String[]) (ActivityThread.java:7000)
        at java.lang.Object java.lang.reflect.Method.invoke(java.lang.Object, java.lang.Object[]) (Method.java:-2)
        at void com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run() (RuntimeInit.java:441)
        at void com.android.internal.os.ZygoteInit.main(java.lang.String[]) (ZygoteInit.java:1408)
java android dynamic
2个回答
1
投票

在科特林，

private fun setButton() {
        val btn = mutableListOf<Button>()
        for( i in 0..3){
            val value = "btn"+(i+1)
            val id = resources.getIdentifier(value,"id",packageName)
            btn.add(findViewById<Button>(id))
        }

    }

使用下面的代码查找视图

val value = "btn"+(i+1)
            val id = resources.getIdentifier(value,"id",packageName)
0
投票

这是@Kishan答案的Java版本

static final int NUM_OF_BUTTONS=10;
List<Button> buttonsList = new ArrayList<>(NUM_OF_BUTTONS);
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.test);

    for( int i=0 ;i<NUM_OF_BUTTONS;i++){
        String value = "btn"+(i+1);
        int id = getResources().getIdentifier(value,"id",getPackageName());
        buttonsList.add((Button) findViewById(id));
    }

}
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