Question

我遇到了btn.setText()的问题，但可以setOnClickListener() logcat告诉我：

java.lang.NullPointerException：尝试调用虚方法＆＃39; void android.widget.TextView.setText（java.lang.CharSequence）＆＃39;在com.gc.materialdesign.views.Button.setText（Button.java:185）上的空对象引用上

我尝试修复但失败了，这是.java代码：

package com.example.rain.fishingcard;

import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;

public class MainActivity extends AppCompatActivity {

com.gc.materialdesign.views.ButtonRectangle startbtn;

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

    startbtn = (com.gc.materialdesign.views.ButtonRectangle) findViewById(R.id.startbtn);

    startbtn.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            //Intent intent = new Intent(MainActivity.this, GameActivity.class);
            //startActivity(intent);
            startbtn.setText("I like");
        }
    });
}
}

，它是.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
xmlns:materialdesign="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
android:paddingBottom="@dimen/activity_vertical_margin"
tools:context="com.example.rain.fishingcard.MainActivity">

<TextView
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="Fishing Card!"
    android:layout_marginTop="59dp"
    android:layout_alignParentTop="true"
    android:layout_centerHorizontal="true"
    android:id="@+id/startText" />

<com.gc.materialdesign.views.ButtonRectangle
    android:id="@+id/startbtn"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:background="#1E88E5"
    android:text="start"
    android:layout_marginTop="48dp"
    android:layout_below="@+id/startText"
    android:layout_alignLeft="@+id/startText"
    android:layout_alignStart="@+id/startText" />

<com.gc.materialdesign.views.ButtonRectangle
    android:id="@+id/settingbtn"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:background="#1E88E5"
    android:text="setting"
    android:visibility="gone"
    android:layout_below="@+id/startbtn"
    android:layout_alignLeft="@+id/startbtn"
    android:layout_alignStart="@+id/startbtn" />
</RelativeLayout>

这是logcat：

  06-19 00:26:23.627 2130-2130/com.example.rain.fishingcard E/AndroidRuntime: FATAL EXCEPTION: 
  main Process: com.example.rain.fishingcard, PID: 2130
  Theme: themes:{}
  java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.TextView.setText(java.lang.CharSequence)' on a null object reference at com.gc.materialdesign.views.Button.setText(Button.java:185)
    at com.example.rain.fishingcard.MainActivity$1.onClick(MainActivity.java:24)
    at com.gc.materialdesign.views.Button.makeCircle(Button.java:135)
    at com.gc.materialdesign.views.ButtonRectangle.onDraw(ButtonRectangle.java:145)
    at android.view.View.draw(View.java:16187)
    at android.view.View.updateDisplayListIfDirty(View.java:15184)
    at android.view.ViewGroup.recreateChildDisplayList(ViewGroup.java:3593)
    at android.view.ViewGroup.dispatchGetDisplayList(ViewGroup.java:3573)
    at android.view.View.updateDisplayListIfDirty(View.java:15144)
    at android.view.ViewGroup.recreateChildDisplayList(ViewGroup.java:3593)
    at android.view.ViewGroup.dispatchGetDisplayList(ViewGroup.java:3573)
    at android.view.View.updateDisplayListIfDirty(View.java:15144)
    at android.view.ViewGroup.recreateChildDisplayList(ViewGroup.java:3593)
    at android.view.ViewGroup.dispatchGetDisplayList(ViewGroup.java:3573)
    at android.view.View.updateDisplayListIfDirty(View.java:15144)
    at android.view.ViewGroup.recreateChildDisplayList(ViewGroup.java:3593)
    at android.view.ViewGroup.dispatchGetDisplayList(ViewGroup.java:3573)
    at android.view.View.updateDisplayListIfDirty(View.java:15144)
    at android.view.ViewGroup.recreateChildDisplayList(ViewGroup.java:3593)
    at android.view.ViewGroup.dispatchGetDisplayList(ViewGroup.java:3573)
    at android.view.View.updateDisplayListIfDirty(View.java:15144)
    at android.view.ViewGroup.recreateChildDisplayList(ViewGroup.java:3593)
    at android.view.ViewGroup.dispatchGetDisplayList(ViewGroup.java:3573)
    at android.view.View.updateDisplayListIfDirty(View.java:15144)
    at android.view.ThreadedRenderer.updateViewTreeDisplayList(ThreadedRenderer.java:282)
    at android.view.ThreadedRenderer.updateRootDisplayList(ThreadedRenderer.java:288)
    at android.view.ThreadedRenderer.draw(ThreadedRenderer.java:323)
    at android.view.ViewRootImpl.draw(ViewRootImpl.java:2623)
    at android.view.ViewRootImpl.performDraw(ViewRootImpl.java:2442)
    at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:2075)
    at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1115)
    at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:6023)
    at android.view.Choreographer$CallbackRecord.run(Choreographer.java:858)
    at android.view.Choreographer.doCallbacks(Choreographer.java:670)
    at android.view.Choreographer.doFrame(Choreographer.java:606)
    at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:844)
    at android.os.Handler.handleCallback(Handler.java:739)
    at android.os.Handler.dispatchMessage(Handler.java:95)
    at android.os.Looper.loop(Looper.java:148)
    at android.app.ActivityThread.main(ActivityThread.java:5461)
    at java.lang.reflect.Method.invoke(Native Method)
    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616) 06-19 00:31:23.342 2130-2130/com.example.rain.fishingcard I/Process: Sending signal. PID: 2130 SIG: 9

Answer 1

请更改您的代码：

 startbtn.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            //Intent intent = new Intent(MainActivity.this, GameActivity.class);
            //startActivity(intent);
            startbtn.setText("I like");
        }
    });

代码：

 startbtn.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            //Intent intent = new Intent(MainActivity.this, GameActivity.class);
            //startActivity(intent);
            TextView textButton = new TextView(getContext());
            textButton.setText("I like");
            startbtn.setText(textButton);
        }
    });

这将解决您的问题。

Answer 2

尝试下载库并将其作为模块导入到您的应用中，然后尝试用这两个类ButtonRectangle和ButtonFlat替换两个类ButtonRectangle.java和ButtonFlat.java然后你很好去吧。

setText（）与com.gc.materialdesign.views.ButtonRectangle，我该如何解决？

2 个答案: