java - 应用程序不断崩溃，在android studio中编程

Question

package kdev.circles;

import android.support.v7.app.ActionBarActivity;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;


public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        final EditText ca = (EditText)findViewById(R.id.ca);
        final EditText cp = (EditText)findViewById(R.id.cp);
        final EditText sv = (EditText)findViewById(R.id.sv);
        final EditText r = (EditText)findViewById(R.id.radius);
        final TextView log = (TextView)findViewById(R.id.log);
        Button clear = (Button)findViewById(R.id.clear);
        Button solve = (Button)findViewById(R.id.Solve);
        clear.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                ca.setText("");
                cp.setText("");
                sv.setText("");
                r.setText("");
            }
        });
        solve.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                if((r.toString()).equals("")) {
                    log.setText(log.getText() + "\n" + "error, no value entered");
                }else{
                    sv.setText(String.valueOf(Double.valueOf(String.valueOf(r.getText())) * Double.valueOf(String.valueOf(r.getText())) * Double.valueOf(String.valueOf(r.getText())) * 4 / 3 * 3.14159265));
                    cp.setText(String.valueOf(Double.valueOf(String.valueOf(r.getText()))*3.14159265*2));
                    ca.setText(String.valueOf(Double.valueOf(String.valueOf(r.getText()))*Double.valueOf(String.valueOf(r.getText()))*3.14159265));
                    log.setText(log.getText()+"\n"+"ca"+ca.getText()+"\n"+"sv"+sv.getText()+"\n"+"cp"+cp.getText());
                }
            }
        });


    }


    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.menu_main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();

        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings) {
            return true;
        }

        return super.onOptionsItemSelected(item);
    }
}

xml文件:

<Button
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="Solve"
    android:id="@+id/Solve"
    android:width="100dp"
    android:layout_alignParentBottom="true"
    android:layout_alignEnd="@+id/sv" />

<EditText
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:inputType="numberDecimal"
    android:ems="10"
    android:id="@+id/radius"
    android:layout_alignParentTop="true"
    android:layout_alignStart="@+id/editText" />

<EditText
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:inputType="numberDecimal"
    android:ems="10"
    android:id="@+id/editText"
    android:layout_alignParentTop="true"
    android:layout_alignParentEnd="true"
    android:layout_marginTop="49dp" />

<EditText
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:inputType="numberDecimal"
    android:ems="10"
    android:id="@+id/editText2"
    android:layout_below="@+id/editText"
    android:layout_alignStart="@+id/editText" />

<EditText
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:inputType="numberDecimal"
    android:ems="10"
    android:id="@+id/editText3"
    android:layout_below="@+id/editText2"
    android:layout_alignStart="@+id/editText2" />

<TextView
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:textAppearance="?android:attr/textAppearanceLarge"
    android:text="circle&apos;s perimeter"
    android:id="@+id/cp"
    android:layout_above="@+id/editText2"
    android:layout_alignParentStart="true" />

<TextView
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:textAppearance="?android:attr/textAppearanceLarge"
    android:text="circle&apos;s area"
    android:id="@+id/ca"
    android:layout_above="@+id/editText3"
    android:layout_alignParentStart="true" />

<TextView
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:textAppearance="?android:attr/textAppearanceLarge"
    android:text="sphere&apos;s volume"
    android:id="@+id/sv"
    android:layout_alignBottom="@+id/editText3"
    android:layout_alignParentStart="true" />

<TextView
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:textAppearance="?android:attr/textAppearanceLarge"
    android:text="radius"
    android:id="@+id/textView3"
    android:layout_alignBottom="@+id/radius"
    android:layout_alignParentStart="true" />

<Button
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="clear"
    android:id="@+id/clear"
    android:layout_alignBottom="@+id/Solve"
    android:layout_alignStart="@+id/editText3" />

<TextView
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:textAppearance="?android:attr/textAppearanceLarge"
    android:text="Large Text"
    android:id="@+id/log"
    android:layout_below="@+id/editText3"
    android:layout_centerHorizontal="true"
    android:layout_marginTop="57dp" />

一切正常，直到我尝试打开它，我找不到错误，因为我的 android 虚拟设备没有正确连接到 android studio。我不确定我应该做什么。我之前确实遇到过另一个问题，但我意识到这是由于我在加载整个布局之前使用了 findviewbyid 函数。我已经解决了这个问题并尝试了一些不同的技术来解决这个问题但没有任何效果。 当我尝试运行该应用程序时它崩溃了，我不确定为什么？ 任何帮助都会有用，谢谢。 这是日志:

12-10 15:21:18.030    1907-1907/kdev.circles W/art﹕ Verification of java.lang.CharSequence android.support.v7.widget.ResourcesWrapper.getQuantityText(int, int) took 123.881364ms
12-10 15:21:18.520    1907-1907/kdev.circles D/AndroidRuntime﹕ Shutting down VM
12-10 15:21:18.520    1907-1907/kdev.circles E/AndroidRuntime﹕ FATAL EXCEPTION: main
    Process: kdev.circles, PID: 1907
    java.lang.RuntimeException: Unable to start activity ComponentInfo{kdev.circles/kdev.circles.MainActivity}: java.lang.ClassCastException: android.support.v7.widget.AppCompatTextView cannot be cast to android.widget.EditText
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2195)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2245)
            at android.app.ActivityThread.access$800(ActivityThread.java:135)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:136)
            at android.app.ActivityThread.main(ActivityThread.java:5017)
            at java.lang.reflect.Method.invoke(Native Method)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
     Caused by: java.lang.ClassCastException: android.support.v7.widget.AppCompatTextView cannot be cast to android.widget.EditText
            at kdev.circles.MainActivity.onCreate(MainActivity.java:21)
            at android.app.Activity.performCreate(Activity.java:5231)
            at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2159)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2245)
            at android.app.ActivityThread.access$800(ActivityThread.java:135)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:136)
            at android.app.ActivityThread.main(ActivityThread.java:5017)
            at java.lang.reflect.Method.invoke(Native Method)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
12-10 15:21:27.230    1907-1907/kdev.circles I/Process﹕ Sending signal. PID: 1907 SIG: 9
12-10 15:21:31.360    2153-2153/kdev.circles D/AndroidRuntime﹕ Shutting down VM
12-10 15:21:31.360    2153-2153/kdev.circles E/AndroidRuntime﹕ FATAL EXCEPTION: main
    Process: kdev.circles, PID: 2153
    java.lang.RuntimeException: Unable to start activity ComponentInfo{kdev.circles/kdev.circles.MainActivity}: java.lang.ClassCastException: android.support.v7.widget.AppCompatTextView cannot be cast to android.widget.EditText
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2195)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2245)
            at android.app.ActivityThread.access$800(ActivityThread.java:135)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:136)
            at android.app.ActivityThread.main(ActivityThread.java:5017)
            at java.lang.reflect.Method.invoke(Native Method)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
     Caused by: java.lang.ClassCastException: android.support.v7.widget.AppCompatTextView cannot be cast to android.widget.EditText
            at kdev.circles.MainActivity.onCreate(MainActivity.java:21)
            at android.app.Activity.performCreate(Activity.java:5231)
            at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2159)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2245)
            at android.app.ActivityThread.access$800(ActivityThread.java:135)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:136)
            at android.app.ActivityThread.main(ActivityThread.java:5017)
            at java.lang.reflect.Method.invoke(Native Method)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)

Answer 1

检查您在 Java 代码中的 View 类型及其在 xml 中的匹配 ID。它们必须是同一类型。

您在 Java 中有 EditText，但在 xml 中匹配的 View id 是 TextView

例如:

final EditText ca = (EditText)findViewById(R.id.ca);

<TextView
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:textAppearance="?android:attr/textAppearanceLarge"
    android:text="circle&apos;s area"
    android:id="@+id/ca"
    android:layout_above="@+id/editText3"
    android:layout_alignParentStart="true" />