Question

我正在尝试练习，这意味着我需要使用按钮从imageView更改图像。整个事情被实施到练习的另一个项目中。

问题是：它在第二种情况下甚至没有打开Toast“测试”。

package de.vogella.android.temperature;

import android.app.Activity;
import android.graphics.drawable.Drawable;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ImageView;
import android.widget.RadioButton;
import android.widget.Toast;

public class MainActivity extends Activity{
  private EditText text;

  @Override
  public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    text = (EditText) findViewById(R.id.editText1);
    Button button1 = (Button) findViewById(R.id.tempbutton);
    Button button2 = (Button) findViewById(R.id.imageconverter);
    OnClickListener listener = new OnClickListener() {
        @Override
        public void onClick(View v) {
            switch (v.getId()) {
                case R.id.tempbutton:
                    button1Click();
                    break;

                case R.id.imageconverter:

                    button2Click();
                    break;
            }
        }
    };
    button1.setOnClickListener(listener);
    button2.setOnClickListener(listener);

  }




  public void button1Click (){
      RadioButton celsiusButton = (RadioButton) findViewById(R.id.radio0);
        RadioButton fahrenheitButton = (RadioButton) findViewById(R.id.radio1);
        if (text.getText().length() == 0) {
        Toast.makeText(this, "Please enter a valid number",
        Toast.LENGTH_LONG).show();
        return;
        }

        float inputValue = Float.parseFloat(text.getText().toString());
        if (celsiusButton.isChecked()) {
        text.setText(String.valueOf(ConverterUtil.convertFahrenheitToCelsius(inputValue)));
        celsiusButton.setChecked(false);
        fahrenheitButton.setChecked(true);
        } else {
        text.setText(String
        .valueOf(ConverterUtil.convertCelsiusToFahrenheit(inputValue)));
        fahrenheitButton.setChecked(false);
        celsiusButton.setChecked(true);
        }
  }

  public void button2Click (){
      ImageView frontImageView = (ImageView) findViewById(R.id.myicon);
        frontImageView.setImageResource(R.drawable.assigned);
        Toast.makeText(this,"done", Toast.LENGTH_LONG).show();
  }
  }

XML文件：

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    android:background="@color/myColor"
    tools:context=".MainActivity" >

    <EditText
        android:id="@+id/editText1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentLeft="true"
        android:layout_alignParentTop="true"
        android:inputType="numberSigned|numberDecimal"
        android:ems="10" >

        <requestFocus />
    </EditText>

    <RadioGroup
        android:id="@+id/radioGroup1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignLeft="@+id/editText1"
        android:layout_below="@+id/editText1" >

        <RadioButton
            android:id="@+id/radio0"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:checked="true"
            android:text="@string/celsius" />

        <RadioButton
            android:id="@+id/radio1"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="@string/fahrenheit" />
    </RadioGroup>

    <Button
        android:id="@+id/tempbutton"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignLeft="@+id/radioGroup1"
        android:layout_below="@+id/radioGroup1"
        android:text="@string/calc"
        android:onClick="onClick" />

    <TextView
        android:id="@+id/textView1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignLeft="@+id/button1"
        android:layout_alignParentBottom="true"
        android:text="@string/author"
        android:textAppearance="?android:attr/textAppearanceSmall" />

    <DigitalClock
        android:id="@+id/digitalClock1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_above="@+id/textView1"
        android:layout_alignLeft="@+id/textView1"
        android:layout_alignRight="@+id/button1"
        android:text="DigitalClock" />

    <Button
        android:id="@+id/imageconverter"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignBaseline="@+id/button1"
        android:layout_alignBottom="@+id/button1"
        android:layout_centerHorizontal="true"
        android:onClick="onClick"
        android:text="Change Image" />

    <ImageView
        android:id="@+id/myicon"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignLeft="@+id/button2"
        android:layout_below="@+id/button2"
        android:src="@drawable/initial" />

</RelativeLayout>

logcat的：

02-25 16:03:00.228: E/AndroidRuntime(1363):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2121)
02-25 16:03:00.228: E/AndroidRuntime(1363):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2245)
02-25 16:03:00.228: E/AndroidRuntime(1363):     at android.app.ActivityThread.access$800(ActivityThread.java:135)
02-25 16:03:00.228: E/AndroidRuntime(1363):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
02-25 16:03:00.228: E/AndroidRuntime(1363):     at android.os.Handler.dispatchMessage(Handler.java:102)
02-25 16:03:00.228: E/AndroidRuntime(1363):     at android.os.Looper.loop(Looper.java:136)
02-25 16:03:00.228: E/AndroidRuntime(1363):     at android.app.ActivityThread.main(ActivityThread.java:5017)
02-25 16:03:00.228: E/AndroidRuntime(1363):     at java.lang.reflect.Method.invokeNative(Native Method)
02-25 16:03:00.228: E/AndroidRuntime(1363):     at java.lang.reflect.Method.invoke(Method.java:515)
02-25 16:03:00.228: E/AndroidRuntime(1363):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
02-25 16:03:00.228: E/AndroidRuntime(1363):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
02-25 16:03:00.228: E/AndroidRuntime(1363):     at dalvik.system.NativeStart.main(Native Method)
02-25 16:03:00.228: E/AndroidRuntime(1363): Caused by: java.lang.NullPointerException
02-25 16:03:00.228: E/AndroidRuntime(1363):     at android.app.Activity.findViewById(Activity.java:1884)
02-25 16:03:00.228: E/AndroidRuntime(1363):     at de.vogella.android.temperature.MainActivity.<init>(MainActivity.java:24)
02-25 16:03:00.228: E/AndroidRuntime(1363):     at java.lang.Class.newInstanceImpl(Native Method)
02-25 16:03:00.228: E/AndroidRuntime(1363):     at java.lang.Class.newInstance(Class.java:1208)
02-25 16:03:00.228: E/AndroidRuntime(1363):     at android.app.Instrumentation.newActivity(Instrumentation.java:1061)
02-25 16:03:00.228: E/AndroidRuntime(1363):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2112)
02-25 16:03:00.228: E/AndroidRuntime(1363):     ... 11 more

Answer 1

你弄错了。你应该找到你的按钮，然后附上听众：

Button button1 = (Button) findViewById(R.id.tempbutton);
Button button2 = (Button) findViewById(R.id.imageconverter);
OnClickListener listener = new OnClickListener() {
    @Override
    public void onClick(View v) {
        switch (v.getId()) {
            case R.id.tempbutton:
                button1Click();
                break;

            case R.id.imageconverter:
                Toast.makeText(this, "test",Toast.LENGTH_LONG).show();
                button2Click();
                break;
        }
    }
};
button1.setOnClickListener(listener);
button2.setOnClickListener(listener);

Answer 2

首先，如果你想这样做，那么你的活动需要实现View.OnClickListener。

接下来，您需要设置按钮的点击监听器，可能在onCreate。例如，<yourButton>.setOnClickListener(this)。

Answer 3

除非您在布局xml中执行此操作，否则您不会设置单击侦听器。您需要实施View.OnClickListener并在每个按钮上调用setOnClickListener。

Answer 4

我认为你的“测试”吐司是不可见的，因为在你展示它之后，你会展示另一个吐司，即“完成”吐司。最后一个可见，对吧？

哦，你的android:onClick="onClick"按钮错过了xml中的imageconverter。

我的开关（view.getId（））不起作用

4 个答案: