自从我开始使用 TextWatcher 以来，我的应用程序一直在崩溃...正如您在下面看到的，我为 3 个 EditText 字段创建了一个 TextWatcher...并且我制作了一个按钮来监听 3 个 EditText .. 如果它们为空，则按钮将被禁用. 填写字段后，按钮应启用..
package com.example.magazijnapp;
import androidx.appcompat.app.AppCompatActivity;
import androidx.appcompat.widget.MenuPopupWindow;
import android.content.DialogInterface;
import android.os.Bundle;
import android.text.Editable;
import android.text.TextWatcher;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Spinner;
import android.widget.SpinnerAdapter;
import android.widget.Switch;
import android.widget.TextView;
import android.widget.Toast;
import org.w3c.dom.Text;
import java.sql.Array;
public class MainActivity extends AppCompatActivity {
Spinner spinnermagazijn;
Button knop;
private EditText EditTextregisternummerbalk;
private EditText EditTextticketnummerbalk;
private EditText EditTextartikelnummerbalk;
private Button knopconfirm;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
EditTextregisternummerbalk = findViewById(R.id.registernummerbalk);
EditTextticketnummerbalk = findViewById(R.id.ticketnummerbalk);
EditTextartikelnummerbalk = findViewById(R.id.artikelnummerbalk);
knopconfirm = findViewById(R.id.knop);
EditTextregisternummerbalk.addTextChangedListener(invulTextWatcher);
EditTextticketnummerbalk.addTextChangedListener(invulTextWatcher);
EditTextartikelnummerbalk.addTextChangedListener(invulTextWatcher);
}
private TextWatcher invulTextWatcher = new TextWatcher() {
@Override
public void beforeTextChanged(CharSequence s, int start, int count, int after) {
}
@Override
public void onTextChanged(CharSequence s, int start, int before, int count) {
String registernummerinput = EditTextregisternummerbalk.getText().toString().trim();
String ticketnummerinput = EditTextticketnummerbalk.getText().toString().trim();
String artikelnummerinput = EditTextartikelnummerbalk.getText().toString().trim();
knopconfirm.setEnabled(!registernummerinput.isEmpty() && !ticketnummerinput.isEmpty() &&! artikelnummerinput.isEmpty());
}
@Override
public void afterTextChanged(Editable s) {
}
};
{
spinnermagazijn = findViewById(R.id.spinnermagazijn);
knop = findViewById(R.id.knop);
populatespinnermagazijn();
// Dit is het stukje voor de Knop afboeken waarmee je een melding genereerd, String aanpassen voor ander resultaat.
knop.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Toast.makeText(MainActivity.this, (R.string.succes), Toast.LENGTH_SHORT) .show();
}
});
}
// Dit gedeelte is voor de spinner.
private void populatespinnermagazijn() {
ArrayAdapter<String> magazijnenAdapter = new ArrayAdapter<>(this, android.R.layout.simple_spinner_item, getResources().getStringArray(R.array.steunpunten));
magazijnenAdapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
spinnermagazijn.setAdapter(magazijnenAdapter);
}
}
这是我的日志...
03-19 21:04:06.293 21151-21151/? E/libprocessgroup: failed to make and chown /acct/uid_10060: Read-only file system
03-19 21:04:06.293 21151-21151/? W/Zygote: createProcessGroup failed, kernel missing CONFIG_CGROUP_CPUACCT?
03-19 21:04:06.293 21151-21151/? I/art: Not late-enabling -Xcheck:jni (already on)
03-19 21:04:06.313 21151-21161/? I/art: Debugger is no longer active
03-19 21:04:06.351 21151-21151/? D/AndroidRuntime: Shutting down VM
03-19 21:04:06.354 21151-21151/? E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.magazijnapp, PID: 21151
java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.example.magazijnapp/com.example.magazijnapp.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'android.content.pm.ApplicationInfo android.content.Context.getApplicationInfo()' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2236)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2387)
at android.app.ActivityThread.access$800(ActivityThread.java:151)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1303)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5254)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'android.content.pm.ApplicationInfo android.content.Context.getApplicationInfo()' on a null object reference
at android.content.ContextWrapper.getApplicationInfo(ContextWrapper.java:149)
at android.view.ContextThemeWrapper.getTheme(ContextThemeWrapper.java:99)
at android.content.Context.obtainStyledAttributes(Context.java:437)
at androidx.appcompat.app.AppCompatDelegateImpl.createSubDecor(AppCompatDelegateImpl.java:692)
at androidx.appcompat.app.AppCompatDelegateImpl.ensureSubDecor(AppCompatDelegateImpl.java:659)
at androidx.appcompat.app.AppCompatDelegateImpl.findViewById(AppCompatDelegateImpl.java:479)
at androidx.appcompat.app.AppCompatActivity.findViewById(AppCompatActivity.java:214)
at com.example.magazijnapp.MainActivity.<init>(MainActivity.java:73)
at java.lang.reflect.Constructor.newInstance(Native Method)
at java.lang.Class.newInstance(Class.java:1606)
at android.app.Instrumentation.newActivity(Instrumentation.java:1066)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2226)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2387)
at android.app.ActivityThread.access$800(ActivityThread.java:151)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1303)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5254)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
03-19 21:04:07.996 21151-21151/? I/Process: Sending signal. PID: 21151 SIG: 9